| 2003-03-31 | @ SLN | 1 | L 9-11 | 0-1 | 6 | 49,561 | Ben Sheets | Matt Morris | Russ Springer | Mike DeJean | Steve Kline | 9 | 11 | -2 |
| 2003-04-02 | @ SLN | 2 | L 0-7 | 0-2 | 6 | 26,790 | Glendon Rusch | Woody Williams | Woody Williams | Glendon Rusch | | 9 | 18 | -9 |
| 2003-04-03 | @ SLN | 3 | L 4-6 | 0-3 | 6 | 26,952 | Matt Kinney | Garrett Stephenson | Garrett Stephenson | Matt Kinney | Steve Kline | 13 | 24 | -11 |
| 2003-04-04 | vs SFN | 4 | L 5-7 | 0-4 | 6 | 42,570 | Todd Ritchie | Ryan Jensen | Jim Brower | Luis Vizcaino | Tim Worrell | 18 | 31 | -13 |
| 2003-04-05 | vs SFN | 5 | L 5-6 | 0-5 | 6 | 16,255 | Ben Sheets | Kurt Ainsworth | Kurt Ainsworth | Ben Sheets | Scott Eyre | 23 | 37 | -14 |
| 2003-04-06 | vs SFN | 6 | L 0-5 | 0-6 | 6 | 16,101 | Wayne Franklin | Kirk Rueter | Kirk Rueter | Wayne Franklin | Jim Brower | 23 | 42 | -19 |
| 2003-04-08 | @ PIT | 7 | W 5-3 | 1-6 | 6 | 36,003 | Glendon Rusch | Kip Wells | Glendon Rusch | Kip Wells | Mike DeJean | 28 | 45 | -17 |
| 2003-04-09 | @ PIT | 8 | W 3-2 | 2-6 | 6 | 23,332 | Todd Ritchie | Josh Fogg | Todd Ritchie | Josh Fogg | Mike DeJean | 31 | 47 | -16 |
| 2003-04-10 | @ PIT | 9 | L 1-3 | 2-7 | 6 | 10,384 | Ben Sheets | Jeff Suppan | Jeff Suppan | Ben Sheets | Mike Williams | 32 | 50 | -18 |
| 2003-04-11 | @ ARI | 10 | W 11-7 | 3-7 | 6 | 31,958 | Wayne Franklin | Randy Johnson | Wayne Franklin | Randy Johnson | | 43 | 57 | -14 |
| 2003-04-12 | @ ARI | 11 | W 3-2 | 4-7 | 6 | 36,835 | Matt Kinney | Curt Schilling | Matt Kinney | Curt Schilling | Mike DeJean | 46 | 59 | -13 |
| 2003-04-13 | @ ARI | 12 | L 3-9 | 4-8 | 6 | 34,416 | Glendon Rusch | Elmer Dessens | Elmer Dessens | Glendon Rusch | | 49 | 68 | -19 |
| 2003-04-14 | vs SLN | 13 | L 5-7 | 4-9 | 6 | 10,684 | Todd Ritchie | Brett Tomko | Brett Tomko | Todd Ritchie | Steve Kline | 54 | 75 | -21 |
| 2003-04-15 | vs SLN | 14 | W 6-1 | 5-9 | 6 | 12,149 | Ben Sheets | Garrett Stephenson | Ben Sheets | Garrett Stephenson | | 60 | 76 | -16 |
| 2003-04-16 | vs SLN | 15 | L 2-15 | 5-10 | 6 | 12,387 | Wayne Franklin | Matt Morris | Matt Morris | Wayne Franklin | | 62 | 91 | -29 |
| 2003-04-17 | vs HOU | 16 | W 4-2 | 6-10 | 5 | 11,022 | Matt Kinney | Tim Redding | Matt Kinney | Tim Redding | Valerio de los Santos | 66 | 93 | -27 |
| 2003-04-18 | vs HOU | 17 | L 5-11 | 6-11 | 5 | 14,867 | Glendon Rusch | Roy Oswalt | Roy Oswalt | Glendon Rusch | | 71 | 104 | -33 |
| 2003-04-19 | vs HOU | 18 | W 3-2 | 7-11 | 5 | 19,239 | Todd Ritchie | Wade Miller | John Foster | Scott Linebrink | | 74 | 106 | -32 |
| 2003-04-20 | vs HOU | 19 | W 5-4 | 8-11 | 5 | 10,125 | Ben Sheets | Jeriome Robertson | Curt Leskanic | Peter Munro | Mike DeJean | 79 | 110 | -31 |
| 2003-04-22 | @ FLO | 20 | L 2-4 | 8-12 | 5 | 10,115 | Wayne Franklin | Brad Penny | Armando Almanza | Valerio de los Santos | Braden Looper | 81 | 114 | -33 |
| 2003-04-23 | @ FLO | 21 | L 4-5 | 8-13 | 5 | 9,182 | Glendon Rusch | Carl Pavano | Armando Almanza | Shane Nance | | 85 | 119 | -34 |
| 2003-04-24 | @ FLO | 22 | L 2-4 | 8-14 | 6 | 9,069 | Todd Ritchie | Mark Redman | Mark Redman | Todd Ritchie | | 87 | 123 | -36 |
| 2003-04-25 | @ ATL | 23 | W 12-5 | 9-14 | 5 | 21,938 | Ben Sheets | Shane Reynolds | Ben Sheets | Shane Reynolds | | 99 | 128 | -29 |
| 2003-04-26 | @ ATL | 24 | L 2-3 | 9-15 | 6 | 27,313 | Wayne Franklin | Horacio Ramirez | Ray King | Valerio de los Santos | John Smoltz | 101 | 131 | -30 |
| 2003-04-27 | @ ATL | 25 | L 1-7 | 9-16 | 6 | 26,349 | Glendon Rusch | Russ Ortiz | Russ Ortiz | Glendon Rusch | | 102 | 138 | -36 |
| 2003-04-29 | vs MON | 26 | L 2-3 | 9-17 | 6 | 10,044 | Matt Kinney | Javier Vazquez | Scott Stewart | Mike DeJean | Rocky Biddle | 104 | 141 | -37 |
| 2003-04-30 | vs MON | 27 | L 5-9 | 9-18 | 6 | 10,945 | Ben Sheets | Livan Hernandez | Livan Hernandez | Ben Sheets | | 109 | 150 | -41 |
| 2003-05-01 | vs MON | 28 | L 0-5 | 9-19 | 6 | 13,180 | Wayne Franklin | Zach Day | Zach Day | Wayne Franklin | | 109 | 155 | -46 |
| 2003-05-02 | vs NYN | 29 | L 3-9 | 9-20 | 6 | 16,315 | Glendon Rusch | Tom Glavine | Tom Glavine | Glendon Rusch | | 112 | 164 | -52 |
| 2003-05-03 | vs NYN | 30 | W 3-2 | 10-20 | 6 | 19,796 | Ruben Quevedo | Jae Weong Seo | John Foster | David Weathers | Mike DeJean | 115 | 166 | -51 |
| 2003-05-04 | vs NYN | 31 | L 3-5 | 10-21 | 6 | 18,571 | Matt Kinney | Al Leiter | Al Leiter | Matt Kinney | Armando Benitez | 118 | 171 | -53 |
| 2003-05-05 | @ CHN | 32 | W 5-3 | 11-21 | 6 | 35,304 | Ben Sheets | Matt Clement | Ben Sheets | Matt Clement | Mike DeJean | 123 | 174 | -51 |
| 2003-05-06 | @ CHN | 33 | W 9-6 | 12-21 | 6 | 34,240 | Wayne Franklin | Mark Prior | Curt Leskanic | Juan Cruz | Mike DeJean | 132 | 180 | -48 |
| 2003-05-07 | @ CHN | 34 | L 1-2 | 12-22 | 6 | 37,574 | Glendon Rusch | Shawn Estes | Shawn Estes | Glendon Rusch | Joe Borowski | 133 | 182 | -49 |
| 2003-05-09 | @ CIN | 35 | L 6-7 | 12-23 | 6 | 26,320 | Matt Kinney | Chris Reitsma | Brian Reith | Luis Vizcaino | | 139 | 189 | -50 |
| 2003-05-10 | @ CIN | 36 | W 9-3 | 13-23 | 6 | 32,554 | Ben Sheets | John Riedling | Ben Sheets | John Riedling | | 148 | 192 | -44 |
| 2003-05-11 | @ CIN | 37 | L 5-7 | 13-24 | 6 | 24,804 | Wayne Franklin | Jeff Austin | Jeff Austin | Wayne Franklin | Scott Williamson | 153 | 199 | -46 |
| 2003-05-12 | vs CHN | 38 | L 5-11 | 13-25 | 6 | 19,106 | Glendon Rusch | Mark Prior | Mark Prior | Glendon Rusch | | 158 | 210 | -52 |
| 2003-05-13 | vs CHN | 39 | L 2-7 | 13-26 | 6 | 18,454 | Ruben Quevedo | Shawn Estes | Shawn Estes | Ruben Quevedo | | 160 | 217 | -57 |
| 2003-05-14 | vs CHN | 40 | L 1-6 | 13-27 | 6 | 27,566 | Matt Kinney | Carlos Zambrano | Carlos Zambrano | Matt Kinney | | 161 | 223 | -62 |
| 2003-05-15 | vs CHN | 41 | L 2-4 | 13-28 | 6 | 31,624 | Ben Sheets | Kerry Wood | Kyle Farnsworth | Brooks Kieschnick | Todd Wellemeyer | 163 | 227 | -64 |
| 2003-05-16 | vs CIN | 42 | W 12-3 | 14-28 | 6 | 13,376 | Wayne Franklin | Ryan Dempster | Wayne Franklin | Ryan Dempster | | 175 | 230 | -55 |
| 2003-05-17 | vs CIN | 43 | W 8-6 | 15-28 | 6 | 16,482 | Glendon Rusch | Jeff Austin | Mike DeJean | Scott Williamson | | 183 | 236 | -53 |
| 2003-05-18 | vs CIN | 44 | L 3-6 | 15-29 | 6 | 14,703 | Ruben Quevedo | Paul Wilson | Scott Sullivan | Mike DeJean | Scott Williamson | 186 | 242 | -56 |
| 2003-05-19 | vs SDN | 45 | W 6-5 | 16-29 | 6 | 10,136 | Matt Kinney | Randy Keisler | Matt Kinney | Randy Keisler | Mike DeJean | 192 | 247 | -55 |
| 2003-05-20 | vs SDN | 46 | W 8-7 | 17-29 | 6 | 11,720 | Ben Sheets | Adam Eaton | Mike DeJean | Matt Herges | | 200 | 254 | -54 |
| 2003-05-21 | vs SDN | 47 | W 10-0 | 18-29 | 6 | 18,138 | Wayne Franklin | Jake Peavy | Wayne Franklin | Jake Peavy | | 210 | 254 | -44 |
| 2003-05-23 | vs LAN | 48 | L 4-6 | 18-30 | 6 | 14,859 | Glendon Rusch | Odalis Perez | Odalis Perez | Glendon Rusch | Guillermo Mota | 214 | 260 | -46 |
| 2003-05-24 | vs LAN | 49 | L 0-6 | 18-31 | 6 | 20,615 | Matt Kinney | Hideo Nomo | Hideo Nomo | Matt Kinney | | 214 | 266 | -52 |
| 2003-05-25 | vs LAN | 50 | L 1-5 | 18-32 | 6 | 22,354 | Ben Sheets | Kevin Brown | Kevin Brown | Ben Sheets | | 215 | 271 | -56 |
| 2003-05-27 | @ SDN | 51 | W 4-2 | 19-32 | 6 | 13,404 | Wayne Franklin | Jake Peavy | Luis Vizcaino | Mike Matthews | Mike DeJean | 219 | 273 | -54 |
| 2003-05-28 | @ SDN | 52 | L 6-8 | 19-33 | 6 | 12,373 | Glendon Rusch | Carlton Loewer | Mike Matthews | Luis Vizcaino | | 225 | 281 | -56 |
| 2003-05-29 | @ SDN | 53 | W 3-2 | 20-33 | 6 | 13,192 | Matt Kinney | Brian Lawrence | Leo Estrella | Brian Lawrence | Mike DeJean | 228 | 283 | -55 |
| 2003-05-30 | @ LAN | 54 | W 5-3 | 21-33 | 6 | 32,452 | Ben Sheets | Hideo Nomo | Ben Sheets | Hideo Nomo | Mike DeJean | 233 | 286 | -53 |
| 2003-05-31 | @ LAN | 55 | L 0-3 | 21-34 | 6 | 35,520 | Ruben Quevedo | Kevin Brown | Kevin Brown | Ruben Quevedo | Eric Gagne | 233 | 289 | -56 |
| 2003-06-01 | @ LAN | 56 | W 4-3 | 22-34 | 6 | 35,611 | Wayne Franklin | Kazuhisa Ishii | Jayson Durocher | Guillermo Mota | Mike DeJean | 237 | 292 | -55 |
| 2003-06-05 | @ NYN | 57 | W 8-7 | 24-34 | 6 | 0 | Matt Kinney | Steve Trachsel | Matt Kinney | Steve Trachsel | Mike DeJean | 245 | 299 | -54 |
| 2003-06-05 | @ NYN | 58 | W 5-3 | 24-34 | 6 | 19,048 | Ben Sheets | Tom Glavine | Ben Sheets | Tom Glavine | Mike DeJean | 250 | 302 | -52 |
| 2003-06-06 | vs BOS | 59 | W 9-3 | 25-34 | 6 | 20,195 | Wayne Franklin | Tim Wakefield | Jayson Durocher | Hector Almonte | | 259 | 305 | -46 |
| 2003-06-07 | vs BOS | 60 | L 10-11 | 25-35 | 6 | 34,242 | Ruben Quevedo | Casey Fossum | Brandon Lyon | Mike DeJean | Mike Timlin | 269 | 316 | -47 |
| 2003-06-08 | vs BOS | 61 | L 1-9 | 25-36 | 6 | 20,784 | Glendon Rusch | Derek Lowe | Derek Lowe | Glendon Rusch | | 270 | 325 | -55 |
| 2003-06-10 | vs FLO | 62 | L 4-12 | 25-37 | 6 | 11,598 | Ben Sheets | Mark Redman | Mark Redman | Ben Sheets | | 274 | 337 | -63 |
| 2003-06-11 | vs FLO | 63 | L 5-6 | 25-38 | 6 | 12,419 | Wayne Franklin | Dontrelle Willis | Dontrelle Willis | Wayne Franklin | Braden Looper | 279 | 343 | -64 |
| 2003-06-12 | vs FLO | 64 | W 6-5 | 26-38 | 5 | 13,075 | Matt Kinney | Carl Pavano | Matt Kinney | Carl Pavano | Mike DeJean | 285 | 348 | -63 |
| 2003-06-13 | @ BAL | 65 | L 2-7 | 26-39 | 5 | 28,085 | Glendon Rusch | Sidney Ponson | Sidney Ponson | Glendon Rusch | | 287 | 355 | -68 |
| 2003-06-14 | @ BAL | 66 | W 8-3 | 27-39 | 5 | 28,290 | Ruben Quevedo | Jason Johnson | Ruben Quevedo | Jason Johnson | | 295 | 358 | -63 |
| 2003-06-15 | @ BAL | 67 | L 4-5 | 27-40 | 6 | 36,109 | Ben Sheets | Rodrigo Lopez | Rodrigo Lopez | Ben Sheets | Jorge Julio | 299 | 363 | -64 |
| 2003-06-16 | vs SLN | 68 | W 9-4 | 28-40 | 5 | 24,951 | Wayne Franklin | Kiko Calero | Curt Leskanic | Cal Eldred | | 308 | 367 | -59 |
| 2003-06-17 | vs SLN | 69 | L 3-12 | 28-41 | 6 | 16,659 | Matt Kinney | Garrett Stephenson | Garrett Stephenson | Matt Kinney | | 311 | 379 | -68 |
| 2003-06-18 | vs SLN | 70 | L 1-9 | 28-42 | 6 | 17,495 | Glendon Rusch | Jason Simontacchi | Jason Simontacchi | Glendon Rusch | | 312 | 388 | -76 |
| 2003-06-19 | vs SLN | 71 | L 4-8 | 28-43 | 6 | 20,776 | Ruben Quevedo | Brett Tomko | Brett Tomko | Ruben Quevedo | Jason Isringhausen | 316 | 396 | -80 |
| 2003-06-20 | vs MIN | 72 | W 3-2 | 29-43 | 6 | 25,175 | Ben Sheets | Brad Radke | Curt Leskanic | Juan Rincon | | 319 | 398 | -79 |
| 2003-06-21 | vs MIN | 73 | W 8-1 | 30-43 | 6 | 30,836 | Wayne Franklin | Kyle Lohse | Wayne Franklin | Kyle Lohse | | 327 | 399 | -72 |
| 2003-06-22 | vs MIN | 74 | L 3-8 | 30-44 | 6 | 25,320 | Matt Kinney | Kenny Rogers | Kenny Rogers | Matt Kinney | | 330 | 407 | -77 |
| 2003-06-24 | @ CHN | 75 | L 1-9 | 30-45 | 6 | 40,389 | Ruben Quevedo | Kerry Wood | Kerry Wood | Ruben Quevedo | | 331 | 416 | -85 |
| 2003-06-25 | @ CHN | 76 | W 12-6 | 31-45 | 6 | 38,357 | Ben Sheets | Shawn Estes | Luis Vizcaino | Todd Wellemeyer | | 343 | 422 | -79 |
| 2003-06-26 | @ CHN | 77 | W 5-3 | 32-45 | 6 | 39,711 | Wayne Franklin | Mark Prior | Leo Estrella | Joe Borowski | Mike DeJean | 348 | 425 | -77 |
| 2003-06-27 | @ MIN | 78 | W 13-1 | 33-45 | 6 | 24,413 | Matt Kinney | Kyle Lohse | Matt Kinney | Kyle Lohse | | 361 | 426 | -65 |
| 2003-06-28 | @ MIN | 79 | L 2-5 | 33-46 | 6 | 27,271 | Dave Burba | Kenny Rogers | Kenny Rogers | Dave Burba | Eddie Guardado | 363 | 431 | -68 |
| 2003-06-29 | @ MIN | 80 | L 4-5 | 33-47 | 6 | 23,357 | Matt Ford | Rick Reed | LaTroy Hawkins | Mike DeJean | | 367 | 436 | -69 |
| 2003-07-01 | @ HOU | 81 | L 5-6 | 33-48 | 6 | 23,407 | Ben Sheets | Wade Miller | Ricky Stone | Mike DeJean | | 372 | 442 | -70 |
| 2003-07-02 | @ HOU | 82 | W 5-3 | 34-48 | 6 | 24,340 | Wayne Franklin | Tim Redding | Valerio de los Santos | Ricky Stone | Leo Estrella | 377 | 445 | -68 |
| 2003-07-03 | @ HOU | 83 | L 3-7 | 34-49 | 6 | 31,379 | Matt Kinney | Jeriome Robertson | Jeriome Robertson | Matt Kinney | Octavio Dotel | 380 | 452 | -72 |
| 2003-07-04 | vs COL | 84 | L 6-8 | 34-50 | 6 | 21,144 | Dave Burba | Aaron Cook | Steve Reed | Leo Estrella | Justin Speier | 386 | 460 | -74 |
| 2003-07-05 | vs COL | 85 | L 8-9 | 34-51 | 6 | 30,731 | Matt Ford | Darren Oliver | Darren Oliver | Matt Ford | Brian Fuentes | 394 | 469 | -75 |
| 2003-07-06 | vs COL | 86 | W 3-1 | 35-51 | 6 | 21,623 | Ben Sheets | Denny Stark | Ben Sheets | Jose Jimenez | Mike DeJean | 397 | 470 | -73 |
| 2003-07-07 | vs PIT | 87 | W 9-2 | 36-51 | 6 | 12,322 | Wayne Franklin | Kip Wells | Wayne Franklin | Kip Wells | | 406 | 472 | -66 |
| 2003-07-08 | vs PIT | 88 | L 7-8 | 36-52 | 6 | 12,425 | Matt Kinney | Josh Fogg | Mike Williams | Mike DeJean | Salomon Torres | 413 | 480 | -67 |
| 2003-07-09 | vs PIT | 89 | W 2-1 | 37-52 | 6 | 22,490 | Glendon Rusch | Kris Benson | Brooks Kieschnick | Joe Beimel | | 415 | 481 | -66 |
| 2003-07-10 | vs PIT | 90 | L 4-5 | 37-53 | 6 | 21,190 | Matt Ford | Jeff Suppan | Jeff Suppan | Matt Ford | | 419 | 486 | -67 |
| 2003-07-11 | vs CIN | 91 | L 1-6 | 37-54 | 6 | 28,130 | Ben Sheets | Ryan Dempster | Ryan Dempster | Ben Sheets | | 420 | 492 | -72 |
| 2003-07-12 | vs CIN | 92 | L 1-5 | 37-55 | 6 | 33,977 | Wayne Franklin | Jimmy Haynes | Jimmy Haynes | Wayne Franklin | | 421 | 497 | -76 |
| 2003-07-13 | vs CIN | 93 | L 8-10 | 37-56 | 6 | 23,632 | Matt Kinney | Danny Graves | Felix Heredia | Leo Estrella | | 429 | 507 | -78 |
| 2003-07-17 | @ PIT | 94 | W 7-5 | 38-56 | 6 | 32,304 | Wayne Franklin | Kris Benson | Wayne Franklin | Kris Benson | Leo Estrella | 436 | 512 | -76 |
| 2003-07-18 | @ PIT | 95 | L 2-7 | 38-57 | 6 | 31,697 | Glendon Rusch | Jeff Suppan | Jeff Suppan | Glendon Rusch | | 438 | 519 | -81 |
| 2003-07-19 | @ PIT | 96 | W 1-0 | 39-57 | 6 | 24,461 | Ben Sheets | Jeff D'Amico | Ben Sheets | Jeff D'Amico | Danny Kolb | 439 | 519 | -80 |
| 2003-07-20 | @ PIT | 97 | L 3-6 | 39-58 | 6 | 22,643 | Matt Ford | Kip Wells | Kip Wells | Matt Ford | Mike Lincoln | 442 | 525 | -83 |
| 2003-07-21 | @ CIN | 98 | L 2-11 | 39-59 | 6 | 22,630 | Matt Kinney | Jose Acevedo | Jose Acevedo | Matt Kinney | | 444 | 536 | -92 |
| 2003-07-22 | @ CIN | 99 | W 6-4 | 40-59 | 6 | 22,336 | Wayne Franklin | Paul Wilson | Wayne Franklin | Paul Wilson | Danny Kolb | 450 | 540 | -90 |
| 2003-07-23 | vs HOU | 100 | L 2-3 | 40-60 | 6 | 22,493 | Glendon Rusch | Roy Oswalt | Mike Gallo | Danny Kolb | Billy Wagner | 452 | 543 | -91 |
| 2003-07-24 | vs HOU | 101 | W 2-1 | 41-60 | 6 | 26,773 | Ben Sheets | Ron Villone | Ben Sheets | Ron Villone | Leo Estrella | 454 | 544 | -90 |
| 2003-07-25 | @ COL | 102 | L 3-7 | 41-61 | 6 | 39,013 | Wes Obermueller | Chin-hui Tsao | Chin-hui Tsao | Wes Obermueller | | 457 | 551 | -94 |
| 2003-07-26 | @ COL | 103 | L 8-13 | 41-62 | 6 | 40,675 | Matt Kinney | Denny Stark | Aaron Cook | Valerio de los Santos | | 465 | 564 | -99 |
| 2003-07-27 | @ COL | 104 | L 1-6 | 41-63 | 6 | 30,108 | Wayne Franklin | Jason Jennings | Jason Jennings | Wayne Franklin | | 466 | 570 | -104 |
| 2003-07-28 | @ NYN | 105 | W 4-2 | 42-63 | 6 | 6,056 | Glendon Rusch | Jae Weong Seo | Leo Estrella | David Weathers | Danny Kolb | 470 | 572 | -102 |
| 2003-07-29 | @ NYN | 106 | W 6-3 | 43-63 | 6 | 22,846 | Ben Sheets | Tom Glavine | Ben Sheets | Dan Wheeler | Mike DeJean | 476 | 575 | -99 |
| 2003-07-30 | @ NYN | 107 | L 0-2 | 43-64 | 6 | 22,389 | Wes Obermueller | Al Leiter | Al Leiter | Wes Obermueller | David Weathers | 476 | 577 | -101 |
| 2003-07-31 | @ NYN | 108 | W 4-3 | 44-64 | 6 | 27,590 | Matt Kinney | Aaron Heilman | Matt Kinney | Aaron Heilman | Danny Kolb | 480 | 580 | -100 |
| 2003-08-01 | @ MON | 109 | L 4-8 | 44-65 | 6 | 6,518 | Wayne Franklin | Tomo Ohka | Tomo Ohka | Wayne Franklin | | 484 | 588 | -104 |
| 2003-08-02 | @ MON | 110 | L 1-7 | 44-66 | 6 | 22,180 | David Manning | Javier Vazquez | Javier Vazquez | David Manning | | 485 | 595 | -110 |
| 2003-08-03 | @ MON | 111 | L 2-4 | 44-67 | 6 | 17,953 | Ben Sheets | Livan Hernandez | Livan Hernandez | Ben Sheets | Rocky Biddle | 487 | 599 | -112 |
| 2003-08-05 | vs ATL | 112 | W 4-3 | 45-67 | 6 | 20,986 | Matt Kinney | Horacio Ramirez | Mike DeJean | Darren Holmes | Danny Kolb | 491 | 602 | -111 |
| 2003-08-06 | vs ATL | 113 | L 2-10 | 45-68 | 6 | 30,010 | Wayne Franklin | Greg Maddux | Greg Maddux | Wayne Franklin | | 493 | 612 | -119 |
| 2003-08-07 | vs ATL | 114 | L 1-7 | 45-69 | 6 | 31,097 | Wes Obermueller | Mike Hampton | Mike Hampton | Wes Obermueller | | 494 | 619 | -125 |
| 2003-08-08 | vs FLO | 115 | L 3-5 | 45-70 | 6 | 25,022 | Ben Sheets | Carl Pavano | Carl Pavano | Ben Sheets | Braden Looper | 497 | 624 | -127 |
| 2003-08-09 | vs FLO | 116 | L 1-7 | 45-71 | 6 | 28,488 | David Manning | Mark Redman | Mark Redman | David Manning | | 498 | 631 | -133 |
| 2003-08-10 | vs FLO | 117 | W 5-4 | 46-71 | 6 | 37,521 | Matt Kinney | Brad Penny | Valerio de los Santos | Brad Penny | Danny Kolb | 503 | 635 | -132 |
| 2003-08-12 | @ PHI | 118 | W 6-3 | 47-71 | 6 | 23,136 | Wayne Franklin | Brandon Duckworth | Wayne Franklin | Brandon Duckworth | Danny Kolb | 509 | 638 | -129 |
| 2003-08-13 | @ PHI | 119 | L 4-11 | 47-72 | 6 | 24,683 | Ben Sheets | Kevin Millwood | Kevin Millwood | Ben Sheets | | 513 | 649 | -136 |
| 2003-08-14 | @ PHI | 120 | L 3-4 | 47-73 | 6 | 23,394 | Wes Obermueller | Randy Wolf | Randy Wolf | Wes Obermueller | Mike Williams | 516 | 653 | -137 |
| 2003-08-15 | @ PIT | 121 | L 3-6 | 47-74 | 6 | 21,096 | Matt Kinney | Nelson Figueroa | Nelson Figueroa | Matt Kinney | Julian Tavarez | 519 | 659 | -140 |
| 2003-08-16 | @ PIT | 122 | W 6-4 | 48-74 | 6 | 28,143 | Doug Davis | Kip Wells | Luis Vizcaino | Mike Lincoln | Danny Kolb | 525 | 663 | -138 |
| 2003-08-17 | @ PIT | 123 | L 2-5 | 48-75 | 6 | 24,092 | Wayne Franklin | Josh Fogg | Josh Fogg | Wayne Franklin | Julian Tavarez | 527 | 668 | -141 |
| 2003-08-19 | vs PHI | 124 | W 6-4 | 49-75 | 6 | 17,028 | Ben Sheets | Kevin Millwood | Mike DeJean | Turk Wendell | Danny Kolb | 533 | 672 | -139 |
| 2003-08-20 | vs PHI | 125 | W 10-1 | 50-75 | 6 | 18,115 | Matt Kinney | Randy Wolf | Matt Kinney | Randy Wolf | | 543 | 673 | -130 |
| 2003-08-21 | vs PHI | 126 | W 5-2 | 51-75 | 6 | 19,885 | Doug Davis | Vicente Padilla | Leo Estrella | Vicente Padilla | Danny Kolb | 548 | 675 | -127 |
| 2003-08-22 | vs PIT | 127 | W 3-2 | 52-75 | 6 | 22,413 | Wayne Franklin | Kip Wells | Wayne Franklin | Kip Wells | Danny Kolb | 551 | 677 | -126 |
| 2003-08-23 | vs PIT | 128 | W 7-6 | 53-75 | 6 | 25,432 | Wes Obermueller | Josh Fogg | Leo Estrella | Mark Corey | | 558 | 683 | -125 |
| 2003-08-24 | vs PIT | 129 | W 10-9 | 54-75 | 6 | 36,238 | Ben Sheets | Brian Meadows | Danny Kolb | Mike Gonzalez | | 568 | 692 | -124 |
| 2003-08-25 | @ CIN | 130 | W 10-6 | 55-75 | 6 | 18,411 | Matt Kinney | Aaron Harang | Matt Kinney | Aaron Harang | Danny Kolb | 578 | 698 | -120 |
| 2003-08-26 | @ CIN | 131 | W 7-1 | 56-75 | 6 | 18,787 | Doug Davis | Dan Serafini | Doug Davis | Dan Serafini | | 585 | 699 | -114 |
| 2003-08-27 | @ CIN | 132 | W 6-2 | 57-75 | 6 | 18,069 | Wayne Franklin | Seth Etherton | Wayne Franklin | Seth Etherton | | 591 | 701 | -110 |
| 2003-08-28 | @ CIN | 133 | W 4-3 | 58-75 | 6 | 21,870 | Wes Obermueller | Paul Wilson | Valerio de los Santos | Chris Reitsma | Danny Kolb | 595 | 704 | -109 |
| 2003-08-29 | @ CHN | 134 | L 2-4 | 58-76 | 6 | 38,215 | Ben Sheets | Matt Clement | Matt Clement | Ben Sheets | | 597 | 708 | -111 |
| 2003-08-30 | @ CHN | 135 | W 9-5 | 59-76 | 6 | 39,805 | Matt Kinney | Shawn Estes | Matt Kinney | Shawn Estes | | 606 | 713 | -107 |
| 2003-08-31 | @ CHN | 136 | W 2-0 | 60-76 | 5 | 38,946 | Doug Davis | Juan Cruz | Doug Davis | Juan Cruz | Danny Kolb | 608 | 713 | -105 |
| 2003-09-01 | vs CIN | 137 | L 4-5 | 60-77 | 6 | 19,588 | Wayne Franklin | Seth Etherton | Seth Etherton | Wayne Franklin | Chris Reitsma | 612 | 718 | -106 |
| 2003-09-02 | vs CIN | 138 | W 4-3 | 61-77 | 5 | 8,703 | Wes Obermueller | Paul Wilson | Luis Vizcaino | Danny Graves | Danny Kolb | 616 | 721 | -105 |
| 2003-09-03 | vs CIN | 139 | W 9-6 | 62-77 | 5 | 10,282 | Luis Martinez | John Bale | Leo Estrella | Scott Randall | Danny Kolb | 625 | 727 | -102 |
| 2003-09-05 | vs CHN | 140 | L 2-4 | 62-78 | 5 | 42,909 | Ben Sheets | Juan Cruz | Juan Cruz | Ben Sheets | Joe Borowski | 627 | 731 | -104 |
| 2003-09-06 | vs CHN | 141 | L 4-8 | 62-79 | 5 | 46,218 | Matt Kinney | Mark Prior | Mark Prior | Matt Kinney | | 631 | 739 | -108 |
| 2003-09-07 | vs CHN | 142 | L 2-9 | 62-80 | 5 | 42,127 | Doug Davis | Kerry Wood | Kerry Wood | Doug Davis | | 633 | 748 | -115 |
| 2003-09-08 | vs HOU | 143 | L 4-8 | 62-81 | 5 | 10,202 | Wayne Franklin | Roy Oswalt | Roy Oswalt | Wayne Franklin | | 637 | 756 | -119 |
| 2003-09-09 | vs HOU | 144 | L 6-7 | 62-82 | 6 | 10,102 | Wes Obermueller | Tim Redding | Brad Lidge | Danny Kolb | Billy Wagner | 643 | 763 | -120 |
| 2003-09-10 | vs HOU | 145 | L 1-3 | 62-83 | 6 | 19,793 | Luis Martinez | Jeriome Robertson | Jeriome Robertson | Luis Martinez | Billy Wagner | 644 | 766 | -122 |
| 2003-09-11 | vs HOU | 146 | W 5-3 | 63-83 | 6 | 11,826 | Ben Sheets | Ron Villone | Ben Sheets | Ron Villone | Danny Kolb | 649 | 769 | -120 |
| 2003-09-12 | @ SFN | 147 | L 2-8 | 63-84 | 6 | 41,015 | Matt Kinney | Jason Schmidt | Jason Schmidt | Matt Kinney | | 651 | 777 | -126 |
| 2003-09-13 | @ SFN | 148 | W 5-4 | 64-84 | 5 | 41,403 | Doug Davis | Sidney Ponson | Doug Davis | Sidney Ponson | Danny Kolb | 656 | 781 | -125 |
| 2003-09-14 | @ SFN | 149 | L 4-5 | 64-85 | 6 | 40,736 | Wayne Franklin | Kevin Correia | Felix Rodriguez | Leo Estrella | | 660 | 786 | -126 |
| 2003-09-15 | @ SLN | 150 | L 2-11 | 64-86 | 6 | 27,925 | Wes Obermueller | Brett Tomko | Brett Tomko | Wes Obermueller | | 662 | 797 | -135 |
| 2003-09-16 | @ SLN | 151 | L 5-6 | 64-87 | 6 | 27,405 | Luis Martinez | Sterling Hitchcock | Sterling Hitchcock | Luis Martinez | Jason Isringhausen | 667 | 803 | -136 |
| 2003-09-17 | @ SLN | 152 | W 7-6 | 65-87 | 6 | 27,567 | Ben Sheets | Garrett Stephenson | Leo Estrella | Jason Isringhausen | Danny Kolb | 674 | 809 | -135 |
| 2003-09-18 | @ SLN | 153 | L 0-13 | 65-88 | 6 | 29,729 | Matt Kinney | Woody Williams | Woody Williams | Matt Kinney | | 674 | 822 | -148 |
| 2003-09-19 | vs ARI | 154 | L 2-3 | 65-89 | 6 | 27,154 | Doug Davis | Randy Johnson | Oscar Villarreal | Shane Nance | Matt Mantei | 676 | 825 | -149 |
| 2003-09-20 | vs ARI | 155 | L 4-10 | 65-90 | 6 | 27,823 | Wayne Franklin | Elmer Dessens | Elmer Dessens | Wayne Franklin | Jose Valverde | 680 | 835 | -155 |
| 2003-09-21 | vs ARI | 156 | W 6-4 | 66-90 | 6 | 30,547 | Wes Obermueller | Curt Schilling | Wes Obermueller | Curt Schilling | Danny Kolb | 686 | 839 | -153 |
| 2003-09-23 | vs SLN | 157 | L 1-5 | 66-91 | 6 | 15,042 | Ben Sheets | Woody Williams | Woody Williams | Ben Sheets | | 687 | 844 | -157 |
| 2003-09-24 | vs SLN | 158 | L 4-8 | 66-92 | 6 | 21,965 | Matt Kinney | Matt Morris | Matt Morris | Matt Kinney | Jason Isringhausen | 691 | 852 | -161 |
| 2003-09-25 | @ HOU | 159 | L 1-6 | 66-93 | 6 | 27,934 | Doug Davis | Tim Redding | Tim Redding | Doug Davis | | 692 | 858 | -166 |
| 2003-09-26 | @ HOU | 160 | W 12-5 | 67-93 | 6 | 37,259 | Wayne Franklin | Jeriome Robertson | Dave Burba | Jeriome Robertson | Glendon Rusch | 704 | 863 | -159 |
| 2003-09-27 | @ HOU | 161 | W 5-2 | 68-93 | 6 | 38,627 | Wes Obermueller | Ron Villone | Wes Obermueller | Ron Villone | Danny Kolb | 709 | 865 | -156 |
| 2003-09-28 | @ HOU | 162 | L 5-8 | 68-94 | 6 | 37,977 | Luis Martinez | Kirk Saarloos | Ricky Stone | Luis Martinez | | 714 | 873 | -159 |