                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                  SCHEDULE 13D
                    Under the Securities Exchange Act of 1934
                               (Amendment No. __)


                              CSK Auto Corporation
--------------------------------------------------------------------------------
                                (Name of Issuer)

                          Common Stock, $.01 par value
--------------------------------------------------------------------------------
                         (Title of class of securities)

                                    125965103
--------------------------------------------------------------------------------
                                 (CUSIP number)

                               Clifton S. Robbins
                             Blue Harbour Group, LP
                         240 Greenwich Avenue, 3rd Floor
                          Greenwich, Connecticut 06830
                                 (203) 422-6540
--------------------------------------------------------------------------------
                  (Name, address and telephone number of person
               authorized to receive notices and communications)

                                January 17, 2006
--------------------------------------------------------------------------------
             (Date of event which requires filing of this statement)


If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
[ ].

<PAGE>
<TABLE>
<CAPTION>

--------------------------------------------------------------------------------         ------------------------------------------
CUSIP No. 125965103                                                               13D                                    Page 2
--------------------------------------------------------------------------------         ------------------------------------------
<S>                             <C>                                                     <C>
--------------------------------------  -------------------------------------------------------------------------------------------
1                                       NAME OF REPORTING PERSON:                                  Blue Harbour Strategic Value
                                                                                                   Partners Master Fund, LP

                                        IRS IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):    98-0450159
--------------------------------------  -------------------------------------------------------------------------------------------
2                                       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:                                 (a)  [ ]
                                                                                                                          (b)  [X]
--------------------------------------  -------------------------------------------------------------------------------------------
3
                                        SEC USE ONLY
--------------------------------------  ---------------------------------------------------------------  --------------------------
4
                                        SOURCE OF FUNDS:                                                 WC
--------------------------------------  -------------------------------------------------------------------------------------------
5
                                        CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM
                                        2(d) OR 2(e):                                                                           [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
6
                                        CITIZENSHIP OR PLACE OF ORGANIZATION:                 Cayman Islands, British West Indies
--------------------------------------  --------------  ---------------------------------------------------------------------------
                                        7               SOLE VOTING POWER:                                       0
          NUMBER OF SHARES

            BENEFICIALLY
              OWNED BY

                EACH
              REPORTING

             PERSON WITH
--------------------------------------  --------------  ----------------------------------------------------------
                                        8               SHARED VOTING POWER:                             2,676,100
--------------------------------------  --------------  ----------------------------------------------------------
                                        9               SOLE DISPOSITIVE POWER:                                  0
--------------------------------------  --------------  ----------------------------------------------------------
                                        10              SHARED DISPOSITIVE POWER:                        2,676,100
--------------------------------------  --------------------------------------------------------------------------
11                                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:    2,676,100
--------------------------------------  --------------------------------------------------------------------------------------------
12                                      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES:                [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
13                                      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):                   6.1%
--------------------------------------  -------------------------------------------------------------------------------------------
14                                      TYPE OF REPORTING PERSON:                                              PN
--------------------------------------  -------------------------------------------------------------------------------------------

                                       2
<PAGE>
--------------------------------------------------------------------------------         ------------------------------------------
CUSIP No. 125965103                                                               13D                                    Page 3
--------------------------------------------------------------------------------         ------------------------------------------

--------------------------------------  --------------------------------------------------------------------------------------------
1                                       NAME OF REPORTING PERSON:                                            Blue Harbour GP, LLC

                                        IRS IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):              20-1590782
--------------------------------------  --------------------------------------------------------------------------------------------
2                                       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:                                 (a)  [ ]
                                                                                                                          (b)  [X]
--------------------------------------  --------------------------------------------------------------------------------------------
3                                       SEC USE ONLY
--------------------------------------  -------------------------------------------------------------------------------------------
4                                       SOURCE OF FUNDS                                                  N/A
--------------------------------------  --------------------------------------------------------------------------------------------
5                                       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM
                                        2(d) or 2(e):                                                                          [ ]
--------------------------------------  --------------------------------------------------------------------------------------------
6                                       CITIZENSHIP OR PLACE OF ORGANIZATION:                             Delaware
--------------------------------------  --------------  ----------------------------------------------------------------------------
                                        7               SOLE VOTING POWER:                                          0
          NUMBER OF SHARES

            BENEFICIALLY
              OWNED BY

                EACH
              REPORTING

             PERSON WITH
--------------------------------------  --------------  -------------------------------------------------------------
                                        8               SHARED VOTING POWER:                                2,676,100
--------------------------------------  --------------  -------------------------------------------------------------
                                        9               SOLE DISPOSITIVE POWER:                                     0
--------------------------------------  --------------  -------------------------------------------------------------
                                        10              SHARED DISPOSITIVE POWER:                           2,676,100
--------------------------------------  -----------------------------------------------------------------------------
11                                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:       2,676,100
--------------------------------------  -------------------------------------------------------------------------------------------
12                                      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES:                  [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
13                                      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):                     6.1%
--------------------------------------  -------------------------------------------------------------------------------------------
14                                      TYPE OF REPORTING PERSON:                                                OO
--------------------------------------  -------------------------------------------------------------------------------------------

                                       3
<PAGE>
--------------------------------------------------------------------------------         ------------------------------------------
CUSIP No. 125965103                                                               13D                                    Page 4
--------------------------------------------------------------------------------         ------------------------------------------

--------------------------------------  -------------------------------------------------------------------------------------------
1                                       NAME OF REPORTING PERSON:                                         Blue Harbour Group, LP

                                        IRS IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):           56-2457376
--------------------------------------  -------------------------------------------------------------------------------------------
2                                       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:                                (a)  [ ]
                                                                                                                         (b)  [X]
--------------------------------------  -------------------------------------------------------------------------------------------
3                                       SEC USE ONLY
--------------------------------------  -------------------------------------------------------------------------------------------
4                                       SOURCE OF FUNDS                                                          N/A
--------------------------------------  -------------------------------------------------------------------------------------------
5                                       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM
                                        2(d) OR 2(e):                                                                         [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
6                                       CITIZENSHIP OR PLACE OF ORGANIZATION:                            Delaware
--------------------------------------  --------------  ---------------------------------------------------------------------------
                                        7               SOLE VOTING POWER:                                            0
          NUMBER OF SHARES

            BENEFICIALLY
              OWNED BY

                EACH
              REPORTING

             PERSON WITH
--------------------------------------  --------------  ---------------------------------------------------------------
                                        8               SHARED VOTING POWER:                                  2,676,100
--------------------------------------  --------------  ---------------------------------------------------------------
                                        9               SOLE DISPOSITIVE POWER:                                       0
--------------------------------------  --------------  ---------------------------------------------------------------
                                        10              SHARED DISPOSITIVE POWER:                             2,676,100
--------------------------------------  -------------------------------------------------------------------------------
11                                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:         2,676,100
--------------------------------------  -------------------------------------------------------------------------------------------
12                                      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES:                [  ]
--------------------------------------  -------------------------------------------------------------------------------------------
13                                      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):                      6.1%
--------------------------------------  -------------------------------------------------------------------------------------------
14                                      TYPE OF REPORTING PERSON:                                                 PN
--------------------------------------  -------------------------------------------------------------------------------------------

                                       4
<PAGE>
--------------------------------------------------------------------------------         ------------------------------------------
CUSIP No. 125965103                                                               13D                                    Page 5
--------------------------------------------------------------------------------         ------------------------------------------

--------------------------------------  -------------------------------------------------------------------------------------------
1                                       NAME OF REPORTING PERSON:                                       Blue Harbour Holdings, LLC

                                        IRS IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):         20-1590711
--------------------------------------  -------------------------------------------------------------------------------------------
2                                       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:                                (a)  [ ]
                                                                                                                         (b)  [X]
--------------------------------------  -------------------------------------------------------------------------------------------
3                                       SEC USE ONLY
--------------------------------------  --------------------------------------------------------------------------------------------
4                                       SOURCE OF FUNDS                                                  N/A
--------------------------------------  --------------------------------------------------------------------------------------------
5
                                        CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM
                                        2(d) or 2(e):                                                                         [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
6                                       CITIZENSHIP OR PLACE OF ORGANIZATION:                           Delaware
--------------------------------------  --------------  ---------------------------------------------------------------------------
                                        7               SOLE VOTING POWER:                                         0
          NUMBER OF SHARES

            BENEFICIALLY
              OWNED BY

                EACH
              REPORTING

             PERSON WITH
--------------------------------------  --------------  ------------------------------------------------------------
                                        8               SHARED VOTING POWER:                               2,676,100
--------------------------------------  --------------  ------------------------------------------------------------
                                        9               SOLE DISPOSITIVE POWER:                                    0
--------------------------------------  --------------  -------------------------------------------------------------
                                        10              SHARED DISPOSITIVE POWER:                           2,676,100
--------------------------------------  -----------------------------------------------------------------------------
11                                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:       2,676,100
--------------------------------------  -------------------------------------------------------------------------------------------
12                                      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES:               [  ]
--------------------------------------  -------------------------------------------------------------------------------------------
13                                      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):                     6.1%
--------------------------------------  -------------------------------------------------------------------------------------------
14                                      TYPE OF REPORTING PERSON:                                                OO
--------------------------------------  -------------------------------------------------------------------------------------------

                                       5
<PAGE>
--------------------------------------------------------------------------------         ------------------------------------------
CUSIP No. 125965103                                                               13D                                    Page 6
--------------------------------------------------------------------------------         ------------------------------------------

--------------------------------------  --------------------------------------------------------------------------------------------
1                                       NAME OF REPORTING PERSON:                                              Clifton S. Robbins

                                        IRS IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):
--------------------------------------  --------------------------------------------------------------------------------------------
2                                       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP:                                 (a)  [ ]
                                                                                                                          (b)  [X]
--------------------------------------  --------------------------------------------------------------------------------------------
3                                       SEC USE ONLY
--------------------------------------  ---------------------------------------------------------------  ---------------------------
4                                       SOURCE OF FUNDS                                                  N/A
--------------------------------------  --------------------------------------------------------------------------------------------
5                                       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM
                                        2(d) or 2(e):                                                                          [ ]
--------------------------------------  --------------------------------------------------------------------------------------------
6                                       CITIZENSHIP OR PLACE OF ORGANIZATION:                United States of America
--------------------------------------  --------------  ----------------------------------------------------------------------------
                                        7               SOLE VOTING POWER:                                         0
          NUMBER OF SHARES

            BENEFICIALLY
              OWNED BY

                EACH
              REPORTING

             PERSON WITH
--------------------------------------  --------------  ------------------------------------------------------------
                                        8               SHARED VOTING POWER:                               2,676,100
--------------------------------------  --------------  ------------------------------------------------------------
                                        9               SOLE DISPOSITIVE POWER:                                    0
--------------------------------------  --------------  -------------------------------------------------------------
                                        10              SHARED DISPOSITIVE POWER:                           2,676,100
--------------------------------------  -----------------------------------------------------------------------------
11                                      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:       2,676,100
--------------------------------------  -----------------------------------------------------------------------------
12                                      CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES:                 [ ]
--------------------------------------  -------------------------------------------------------------------------------------------
13                                      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11):                      6.1%
--------------------------------------  --------------------------------------------------------------------------------------------
14                                      TYPE OF REPORTING PERSON:                                                 IN
--------------------------------------  -------------------------------------------------------------------------------------------
</TABLE>

                                       6
<PAGE>
ITEM 1.  SECURITY AND ISSUER.

The title and class of equity security to which this Statement on Schedule 13D
relates is the common stock, par value $0.01 per share ("Common Stock"), of CSK
Auto Corporation, a Delaware corporation (the "Company"). The address of the
Company's principal executive offices is 645 E. Missouri Avenue, Suite 400,
Phoenix, Arizona 85012.

ITEM 2.  IDENTITY AND BACKGROUND.

This Statement is being filed by and on behalf of Blue Harbour Strategic Value
Partners Master Fund, LP, a Cayman Islands exempted limited partnership (the
"Fund"), Blue Harbour GP, LLC, a Delaware limited liability company ("Fund GP"),
Blue Harbour Group, LP, a Delaware limited partnership ("Manager"), Blue Harbour
Holdings, LLC, a Delaware limited liability company ("Manager GP"), and Clifton
S. Robbins, a citizen of the United States of America ("Mr. Robbins"). The Fund,
Fund GP, Manager, Manager GP and Mr. Robbins are herein sometimes referred to
each as a "Reporting Person" and collectively as the "Reporting Persons."

The address of the principal office of each of the Fund, Manager, Manager GP and
Fund GP is 240 Greenwich Avenue, 3rd Floor, Greenwich, Connecticut 06830, and
Mr. Robbins' business address is c/o Manager at the foregoing address. Mr.
Robbins is the Chief Executive Officer of Manager.

The Fund is principally involved in the business of investing in securities.
Fund GP is principally involved in the business of serving as the general
partner of the Fund. Manager is principally involved in the business of
providing investment advisory and investment management services to the Fund and
its affiliates and, among other things, exercises all voting and other powers
and privileges attributable to any securities held for the Fund's account.
Manager GP is principally involved in the business of serving as the general
partner of Manager.

During the last five years, none of the Reporting Persons nor, to the best of
their knowledge, any of their officers and directors, has (i) been convicted in
a criminal proceeding (excluding traffic violations or similar misdemeanors) or
(ii) been a party to a civil proceeding of a judicial or administrative body of
competent jurisdiction and as a result of such proceeding was or is subject to a
judgment, decree or final order enjoining future violations of, or prohibiting
or mandating activities subject to, federal or state securities laws or finding
any violation with respect to such laws.

ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

The 2,676,100 shares of Common Stock reported herein by the Reporting Persons
were acquired by the Fund for an aggregate purchase price of approximately
$39,754,175. The shares of Common Stock that are reported on this Statement on
Schedule 13D were acquired with the Fund's working capital.

ITEM 4.  PURPOSE OF TRANSACTION.

           The Reporting Persons have acquired the Company's Common Stock for
investment purposes, and such purchases have been made in the Reporting Persons'
ordinary course of business.

           In pursuing such investment purposes, the Reporting Persons may
further purchase, hold, vote, trade, dispose or otherwise deal in the securities
of the Company at times, and in such manner, as they deem advisable to benefit
from changes in market prices of such securities, changes in the Company's


                                       7
<PAGE>
operations, business strategy or prospects, or from a sale or merger of the
Company. To evaluate such alternatives, the Reporting Persons will routinely
monitor the Company's operations, prospects, business development, management,
competitive and strategic matters, capital structure, and prevailing market
conditions, as well as alternative investment opportunities, liquidity
requirements of the Reporting Persons and other investment considerations.

           Consistent with its investment research process, the Reporting
Persons may engage in communications regarding such matters with management or
Directors of the Company, other current or prospective shareholders, industry
analysts, existing or potential strategic partners or competitors, investment
and financing professionals, sources of credit and other investors. Such factors
and discussions may materially affect, and result in, the Reporting Persons'
modifying their ownership of securities of the Company, exchanging information
with the Company pursuant to appropriate confidentiality or similar agreements,
proposing changes in the Company's operations, governance or capitalization, or
in proposing one or more of the other actions described in subsections (a)
through (j) of Item 4 of Schedule 13D.

           The Reporting Persons reserve the right to formulate other plans
and/or make other proposals, and take such actions with respect to their
investment in the Company, including any or all of the actions set forth in
paragraphs (a) through (j) of Item 4 of Schedule 13D, or acquire additional
securities of the Company or dispose of all the securities of the Company
beneficially owned by them, in public market or privately negotiated
transactions. The Reporting Persons may at any time reconsider and change their
plans or proposals relating to the foregoing.

ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER.

           (a) - (b) The responses of the Reporting Persons to Rows (7) through
(13) of the cover pages of this Statement on Schedule 13D are incorporated
herein by reference. As of January 26, 2006, the Fund beneficially owned
2,676,100 shares of Common Stock, representing approximately 6.1% of the
outstanding shares of Common Stock (such percentage being based on the number of
shares of Common Stock outstanding as of December 2, 2005 as set forth in the
Company's Report on Form 10-Q for the quarterly period ended October 30, 2005).

           The Fund is the direct owner of the shares of Common Stock reported
on this Statement on Schedule 13D. For purposes of disclosing the number of
shares beneficially owned by each of the Reporting Persons, Fund GP, as general
partner of the Fund, Manager, as the investment manager of the Fund, Manager GP
as the general partner of Manager, and Mr. Robbins, as controlling owner of Fund
GP and Manager GP (in addition to serving as Chief Executive Officer of Manager)
may be deemed to own beneficially (as that term is defined in Rule 13d-3 under
the Securities Exchange Act of 1934) all shares of the Common Stock that are
owned beneficially and directly by the Fund. Fund GP, Manager, Manager GP and
Mr. Robbins disclaims beneficial ownership of such shares for all other
purposes.


           (c) The following table sets forth all transactions with respect to
shares of Common Stock effected during the past sixty (60) days by any of the
Reporting Persons. All such transactions were effected in the open market,
unless otherwise noted.


                                       8
<PAGE>
                         Number of
  Reporting Person    Shares Purchased    Price Per Share          Date
  ----------------    ----------------    ---------------          ----

       Fund               500,000             $15.35           January 17, 2006
       Fund                31,100             $15.50           January 23, 2006


           (d) Not applicable.

           (e) Not applicable.

ITEM 6.    CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
           TO SECURITIES OF THE ISSUER.

           Except as set forth herein, there are no contracts, arrangements,
understandings or relationships among the persons named in Item 2 or between
such persons and any other person with respect to the Common Stock.

           In November 2005, in connection with the evaluation of the Fund's
proposed participation in a financing for the Company that was not ultimately
consummated, Manager and the Company entered into an agreement that contained
confidentiality and other restrictions customary for agreements in similar
circumstances.

ITEM 7.    MATERIAL TO BE FILED AS EXHIBITS.

EXHIBIT 1      Agreement as to Joint Filing of Schedule 13D, dated January 26,
               2006, by and among the Fund, Fund GP, Manager, Manager GP and Mr.
               Robbins.








                                       9
<PAGE>
                                   SIGNATURES

           After reasonable inquiry and to the best of my knowledge and belief,
the undersigned certifies that the information set forth in this statement is
true, complete and correct.



January 26, 2006                              BLUE HARBOUR STRATEGIC VALUE
                                              PARTNERS MASTER FUND, LP

                                              By:  Blue Harbour GP, LLC,
                                                   its general partner

                                                   By:  /s/ Clifton S. Robbins
                                                        ------------------------
                                                   Name:   Clifton S. Robbins
                                                   Title:  Managing Member


January 26, 2006                              BLUE HARBOUR GP, LLC

                                              By:    /s/ Clifton S. Robbins
                                                     ---------------------------
                                              Name:  Clifton S. Robbins
                                              Title: Managing Member


January 26, 2006                              BLUE HARBOUR GROUP, LP

                                              By:  Blue Harbour Holdings, LLC,
                                                   its general partner

                                                   By:    /s/ Clifton S. Robbins
                                                          ----------------------
                                                   Name:  Clifton S. Robbins
                                                   Title: Managing Member


January 26, 2006                              BLUE HARBOUR HOLDINGS, LLC

                                              By:    /s/ Clifton S. Robbins
                                                     ---------------------------
                                              Name:  Clifton S. Robbins
                                              Title: Managing Member


January 26, 2006                              /s/ Clifton S. Robbins
                                              ----------------------------------
                                              Name: Clifton S. Robbins



                                       10
