| 2003-03-31 | @ DET | 1 | W 3-1 | 1-0 | 2 | 40,427 | Brad Radke | Mike Maroth | Brad Radke | Mike Maroth | Eddie Guardado | 3 | 1 | 2 |
| 2003-04-02 | @ DET | 2 | W 8-1 | 2-0 | 2 | 21,123 | Joe Mays | Jeremy Bonderman | Joe Mays | Jeremy Bonderman | | 11 | 2 | 9 |
| 2003-04-03 | @ DET | 3 | W 3-0 | 3-0 | 2 | 8,862 | Kyle Lohse | Adam Bernero | Kyle Lohse | Adam Bernero | Eddie Guardado | 14 | 2 | 12 |
| 2003-04-04 | vs TOR | 4 | L 2-7 | 3-1 | 2 | 48,617 | Rick Reed | Tanyon Sturtze | Tanyon Sturtze | Rick Reed | | 16 | 9 | 7 |
| 2003-04-05 | vs TOR | 5 | L 3-4 | 3-2 | 2 | 31,421 | Kenny Rogers | Roy Halladay | Pete Walker | Eddie Guardado | Kelvim Escobar | 19 | 13 | 6 |
| 2003-04-06 | vs TOR | 6 | L 1-8 | 3-3 | 3 | 23,549 | Brad Radke | Cory Lidle | Cory Lidle | Brad Radke | | 20 | 21 | -1 |
| 2003-04-08 | @ NYA | 7 | L 3-7 | 3-4 | 3 | 33,109 | Joe Mays | Andy Pettitte | Andy Pettitte | Joe Mays | | 23 | 28 | -5 |
| 2003-04-09 | @ NYA | 8 | L 1-2 | 3-5 | 4 | 31,898 | Kyle Lohse | Mike Mussina | Mike Mussina | Kyle Lohse | Juan Acevedo | 24 | 30 | -6 |
| 2003-04-10 | @ NYA | 9 | L 0-2 | 3-6 | 4 | 29,255 | Rick Reed | David Wells | David Wells | Rick Reed | | 24 | 32 | -8 |
| 2003-04-11 | @ TOR | 10 | W 6-4 | 4-6 | 3 | 13,237 | Kenny Rogers | Cory Lidle | Kenny Rogers | Cory Lidle | Eddie Guardado | 30 | 36 | -6 |
| 2003-04-12 | @ TOR | 11 | W 9-6 | 5-6 | 3 | 14,118 | Brad Radke | Pete Walker | LaTroy Hawkins | Kelvim Escobar | Eddie Guardado | 39 | 42 | -3 |
| 2003-04-13 | @ TOR | 12 | W 9-3 | 6-6 | 3 | 13,333 | Joe Mays | Mark Hendrickson | Joe Mays | Mark Hendrickson | | 48 | 45 | 3 |
| 2003-04-15 | vs DET | 13 | W 6-4 | 7-6 | 3 | 14,036 | Kyle Lohse | Mike Maroth | Kyle Lohse | Mike Maroth | Eddie Guardado | 54 | 49 | 5 |
| 2003-04-16 | vs DET | 14 | W 4-2 | 8-6 | 3 | 13,503 | Rick Reed | Adam Bernero | Rick Reed | Adam Bernero | Eddie Guardado | 58 | 51 | 7 |
| 2003-04-17 | vs DET | 15 | W 6-0 | 9-6 | 3 | 13,015 | Kenny Rogers | Jeremy Bonderman | Kenny Rogers | Jeremy Bonderman | | 64 | 51 | 13 |
| 2003-04-18 | vs NYA | 16 | L 4-11 | 9-7 | 3 | 37,843 | Brad Radke | Roger Clemens | Roger Clemens | Brad Radke | | 68 | 62 | 6 |
| 2003-04-19 | vs NYA | 17 | L 2-4 | 9-8 | 3 | 36,139 | Joe Mays | Andy Pettitte | Andy Pettitte | Joe Mays | Juan Acevedo | 70 | 66 | 4 |
| 2003-04-20 | vs NYA | 18 | L 2-8 | 9-9 | 3 | 18,818 | Kyle Lohse | Mike Mussina | Mike Mussina | Kyle Lohse | | 72 | 74 | -2 |
| 2003-04-21 | vs NYA | 19 | L 1-15 | 9-10 | 3 | 20,845 | Rick Reed | David Wells | David Wells | Rick Reed | | 73 | 89 | -16 |
| 2003-04-22 | @ KCA | 20 | L 3-4 | 9-11 | 3 | 17,439 | Kenny Rogers | Runelvys Hernandez | Runelvys Hernandez | Kenny Rogers | Mike MacDougal | 76 | 93 | -17 |
| 2003-04-24 | @ KCA | 21 | L 1-2 | 9-12 | 3 | 11,981 | Brad Radke | Chris George | Chris George | Brad Radke | Mike MacDougal | 77 | 95 | -18 |
| 2003-04-25 | @ CHA | 22 | W 6-1 | 10-12 | 3 | 14,285 | Joe Mays | Mark Buehrle | Joe Mays | Mark Buehrle | | 83 | 96 | -13 |
| 2003-04-26 | @ CHA | 23 | L 4-7 | 10-13 | 3 | 25,381 | Kyle Lohse | Jon Garland | Jon Garland | Kyle Lohse | | 87 | 103 | -16 |
| 2003-04-27 | @ CHA | 24 | L 1-3 | 10-14 | 3 | 22,714 | Rick Reed | Esteban Loaiza | Esteban Loaiza | Rick Reed | Damaso Marte | 88 | 106 | -18 |
| 2003-04-29 | vs TBA | 25 | W 5-3 | 11-14 | 3 | 12,188 | Kenny Rogers | Jorge Sosa | Kenny Rogers | Jorge Sosa | Eddie Guardado | 93 | 109 | -16 |
| 2003-04-30 | vs TBA | 26 | W 8-5 | 12-14 | 3 | 15,282 | Brad Radke | Seth McClung | Brad Radke | Seth McClung | | 101 | 114 | -13 |
| 2003-05-01 | vs TBA | 27 | W 6-5 | 13-14 | 3 | 13,285 | Joe Mays | Steve Parris | Tony Fiore | Travis Harper | | 107 | 119 | -12 |
| 2003-05-02 | @ BOS | 28 | W 11-7 | 14-14 | 3 | 31,317 | Kyle Lohse | John Burkett | Johan Santana | Ramiro Mendoza | | 118 | 126 | -8 |
| 2003-05-03 | @ BOS | 29 | L 1-9 | 14-15 | 3 | 33,061 | Rick Reed | Pedro Martinez | Pedro Martinez | Tony Fiore | | 119 | 135 | -16 |
| 2003-05-04 | @ BOS | 30 | W 9-4 | 15-15 | 2 | 32,887 | Kenny Rogers | Tim Wakefield | Kenny Rogers | Mike Timlin | | 128 | 139 | -11 |
| 2003-05-06 | @ TBA | 31 | W 7-3 | 16-15 | 2 | 8,709 | Brad Radke | Steve Parris | Brad Radke | Steve Parris | | 135 | 142 | -7 |
| 2003-05-07 | @ TBA | 32 | W 11-6 | 17-15 | 2 | 8,654 | Joe Mays | Joe Kennedy | Juan Rincon | Joe Kennedy | | 146 | 148 | -2 |
| 2003-05-08 | @ TBA | 33 | W 5-0 | 18-15 | 2 | 8,699 | Kyle Lohse | Dewon Brazelton | Kyle Lohse | Dewon Brazelton | | 151 | 148 | 3 |
| 2003-05-09 | vs BOS | 34 | W 5-0 | 19-15 | 2 | 28,436 | Johan Santana | Pedro Martinez | Johan Santana | Pedro Martinez | | 156 | 148 | 8 |
| 2003-05-10 | vs BOS | 35 | L 5-6 | 19-16 | 2 | 26,346 | Kenny Rogers | Tim Wakefield | Tim Wakefield | Juan Rincon | Brandon Lyon | 161 | 154 | 7 |
| 2003-05-11 | vs BOS | 36 | W 9-8 | 20-16 | 2 | 15,641 | Brad Radke | Derek Lowe | Brad Radke | Derek Lowe | Eddie Guardado | 170 | 162 | 8 |
| 2003-05-12 | vs KCA | 37 | L 2-3 | 20-17 | 2 | 12,199 | Joe Mays | Jeremy Affeldt | Jeremy Affeldt | Joe Mays | Mike MacDougal | 172 | 165 | 7 |
| 2003-05-13 | vs KCA | 38 | W 4-2 | 21-17 | 2 | 13,898 | Kyle Lohse | Kyle Snyder | LaTroy Hawkins | Albie Lopez | | 176 | 167 | 9 |
| 2003-05-14 | vs KCA | 39 | W 7-0 | 22-17 | 2 | 15,148 | Rick Reed | Runelvys Hernandez | Rick Reed | Runelvys Hernandez | | 183 | 167 | 16 |
| 2003-05-15 | vs KCA | 40 | L 5-9 | 22-18 | 2 | 17,219 | Kenny Rogers | Miguel Asencio | D.J. Carrasco | Johan Santana | | 188 | 176 | 12 |
| 2003-05-16 | vs CHA | 41 | W 18-3 | 23-18 | 2 | 22,233 | Brad Radke | Mark Buehrle | Brad Radke | Mark Buehrle | | 206 | 179 | 27 |
| 2003-05-17 | vs CHA | 42 | W 3-1 | 24-18 | 2 | 23,209 | Joe Mays | Jon Garland | Joe Mays | Jon Garland | Eddie Guardado | 209 | 180 | 29 |
| 2003-05-18 | vs CHA | 43 | W 3-2 | 25-18 | 1 | 25,055 | Kyle Lohse | Esteban Loaiza | LaTroy Hawkins | Tom Gordon | Eddie Guardado | 212 | 182 | 30 |
| 2003-05-20 | @ OAK | 44 | L 1-4 | 25-19 | 1 | 13,340 | Rick Reed | Tim Hudson | Tim Hudson | Rick Reed | Keith Foulke | 213 | 186 | 27 |
| 2003-05-21 | @ OAK | 45 | W 4-3 | 26-19 | 1 | 27,189 | Kenny Rogers | Barry Zito | LaTroy Hawkins | Chad Bradford | Eddie Guardado | 217 | 189 | 28 |
| 2003-05-22 | @ OAK | 46 | W 6-5 | 27-19 | 1 | 27,684 | Joe Mays | John Halama | Joe Mays | John Halama | Eddie Guardado | 223 | 194 | 29 |
| 2003-05-23 | @ SEA | 47 | L 2-5 | 27-20 | 1 | 40,258 | Brad Radke | Jamie Moyer | Jamie Moyer | Brad Radke | Kazuhiro Sasaki | 225 | 199 | 26 |
| 2003-05-24 | @ SEA | 48 | W 7-2 | 28-20 | 1 | 45,306 | Kyle Lohse | Joel Pineiro | Kyle Lohse | Joel Pineiro | | 232 | 201 | 31 |
| 2003-05-25 | @ SEA | 49 | W 3-1 | 29-20 | 1 | 45,213 | Rick Reed | Ryan Franklin | Rick Reed | Ryan Franklin | Eddie Guardado | 235 | 202 | 33 |
| 2003-05-27 | vs OAK | 50 | W 4-3 | 30-20 | 1 | 17,082 | Kenny Rogers | Barry Zito | J.C. Romero | Barry Zito | Eddie Guardado | 239 | 205 | 34 |
| 2003-05-28 | vs OAK | 51 | W 6-5 | 31-20 | 1 | 23,080 | Joe Mays | John Halama | Joe Mays | John Halama | Eddie Guardado | 245 | 210 | 35 |
| 2003-05-29 | vs SEA | 52 | L 6-10 | 31-21 | 1 | 16,409 | Brad Radke | Gil Meche | Gil Meche | Brad Radke | | 251 | 220 | 31 |
| 2003-05-30 | vs SEA | 53 | L 0-6 | 31-22 | 1 | 30,179 | Kyle Lohse | Joel Pineiro | Joel Pineiro | Kyle Lohse | | 251 | 226 | 25 |
| 2003-05-31 | vs SEA | 54 | L 2-5 | 31-23 | 1 | 22,995 | Rick Reed | Ryan Franklin | Ryan Franklin | Rick Reed | Kazuhiro Sasaki | 253 | 231 | 22 |
| 2003-06-01 | vs SEA | 55 | L 5-9 | 31-24 | 1 | 18,754 | Kenny Rogers | Freddy Garcia | Freddy Garcia | Kenny Rogers | | 258 | 240 | 18 |
| 2003-06-03 | @ SFN | 56 | W 6-4 | 32-24 | 1 | 34,713 | Joe Mays | Damian Moss | Joe Mays | Damian Moss | Eddie Guardado | 264 | 244 | 20 |
| 2003-06-04 | @ SFN | 57 | L 3-4 | 32-25 | 1 | 35,319 | Brad Radke | Jerome Williams | Tim Worrell | Juan Rincon | | 267 | 248 | 19 |
| 2003-06-05 | @ SFN | 58 | W 5-2 | 33-25 | 1 | 35,783 | Kyle Lohse | Jesse Foppert | Kyle Lohse | Jesse Foppert | Eddie Guardado | 272 | 250 | 22 |
| 2003-06-06 | @ SDN | 59 | W 7-5 | 34-25 | 1 | 54,747 | Kenny Rogers | Jake Peavy | J.C. Romero | Rod Beck | | 279 | 255 | 24 |
| 2003-06-07 | @ SDN | 60 | W 6-2 | 35-25 | 1 | 31,617 | Johan Santana | Carlton Loewer | Johan Santana | Carlton Loewer | Micheal Nakamura | 285 | 257 | 28 |
| 2003-06-08 | @ SDN | 61 | L 4-9 | 35-26 | 1 | 19,140 | Joe Mays | Brian Lawrence | Brian Lawrence | LaTroy Hawkins | | 289 | 266 | 23 |
| 2003-06-10 | vs COL | 62 | L 0-5 | 35-27 | 1 | 18,886 | Brad Radke | Jason Jennings | Jason Jennings | Brad Radke | | 289 | 271 | 18 |
| 2003-06-11 | vs COL | 63 | W 7-4 | 36-27 | 1 | 17,942 | Kyle Lohse | Aaron Cook | Kyle Lohse | Aaron Cook | Eddie Guardado | 296 | 275 | 21 |
| 2003-06-12 | vs COL | 64 | W 15-3 | 37-27 | 1 | 18,003 | Kenny Rogers | Darren Oliver | Kenny Rogers | Darren Oliver | | 311 | 278 | 33 |
| 2003-06-13 | vs ARI | 65 | W 3-1 | 38-27 | 1 | 26,620 | Johan Santana | Brandon Webb | Johan Santana | Brandon Webb | Eddie Guardado | 314 | 279 | 35 |
| 2003-06-14 | vs ARI | 66 | L 2-9 | 38-28 | 1 | 30,200 | Joe Mays | Miguel Batista | Miguel Batista | Joe Mays | | 316 | 288 | 28 |
| 2003-06-15 | vs ARI | 67 | L 8-12 | 38-29 | 1 | 30,076 | Brad Radke | Elmer Dessens | Mike Koplove | LaTroy Hawkins | | 324 | 300 | 24 |
| 2003-06-16 | @ KCA | 68 | L 8-9 | 38-30 | 1 | 13,442 | Kyle Lohse | Darrell May | Mike MacDougal | Eddie Guardado | | 332 | 309 | 23 |
| 2003-06-17 | @ KCA | 69 | L 7-14 | 38-31 | 1 | 16,359 | Kenny Rogers | Jeremy Affeldt | Kris Wilson | Kenny Rogers | | 339 | 323 | 16 |
| 2003-06-18 | @ KCA | 70 | L 6-8 | 38-32 | 1 | 21,581 | Rick Reed | Chris George | Chris George | Rick Reed | Mike MacDougal | 345 | 331 | 14 |
| 2003-06-19 | @ KCA | 71 | W 16-2 | 39-32 | 1 | 22,559 | Joe Mays | Kyle Snyder | Joe Mays | Kyle Snyder | | 361 | 333 | 28 |
| 2003-06-20 | @ MIL | 72 | L 2-3 | 39-33 | 1 | 25,175 | Brad Radke | Ben Sheets | Curt Leskanic | Juan Rincon | | 363 | 336 | 27 |
| 2003-06-21 | @ MIL | 73 | L 1-8 | 39-34 | 1 | 30,836 | Kyle Lohse | Wayne Franklin | Wayne Franklin | Kyle Lohse | | 364 | 344 | 20 |
| 2003-06-22 | @ MIL | 74 | W 8-3 | 40-34 | 1 | 25,320 | Kenny Rogers | Matt Kinney | Kenny Rogers | Matt Kinney | | 372 | 347 | 25 |
| 2003-06-24 | vs CHA | 75 | L 1-2 | 40-35 | 2 | 19,229 | Rick Reed | Esteban Loaiza | Esteban Loaiza | Rick Reed | Billy Koch | 373 | 349 | 24 |
| 2003-06-25 | vs CHA | 76 | W 6-5 | 41-35 | 2 | 21,338 | Joe Mays | Jon Garland | Eddie Guardado | Billy Koch | | 379 | 354 | 25 |
| 2003-06-26 | vs CHA | 77 | L 1-5 | 41-36 | 2 | 26,474 | Brad Radke | Mark Buehrle | Mark Buehrle | Brad Radke | | 380 | 359 | 21 |
| 2003-06-27 | vs MIL | 78 | L 1-13 | 41-37 | 2 | 24,413 | Kyle Lohse | Matt Kinney | Matt Kinney | Kyle Lohse | | 381 | 372 | 9 |
| 2003-06-28 | vs MIL | 79 | W 5-2 | 42-37 | 2 | 27,271 | Kenny Rogers | Dave Burba | Kenny Rogers | Dave Burba | Eddie Guardado | 386 | 374 | 12 |
| 2003-06-29 | vs MIL | 80 | W 5-4 | 43-37 | 2 | 23,357 | Rick Reed | Matt Ford | LaTroy Hawkins | Mike DeJean | | 391 | 378 | 13 |
| 2003-06-30 | @ CHA | 81 | L 3-10 | 43-38 | 1 | 29,945 | Joe Mays | Jon Garland | Jon Garland | Joe Mays | | 394 | 388 | 6 |
| 2003-07-01 | @ CHA | 82 | L 1-6 | 43-39 | 2 | 30,694 | Brad Radke | Mark Buehrle | Mark Buehrle | Brad Radke | | 395 | 394 | 1 |
| 2003-07-02 | @ CHA | 83 | L 6-8 | 43-40 | 2 | 19,555 | Kyle Lohse | Dan Wright | Billy Koch | Eddie Guardado | | 401 | 402 | -1 |
| 2003-07-03 | vs CLE | 84 | L 1-4 | 43-41 | 2 | 15,064 | Kenny Rogers | CC Sabathia | CC Sabathia | Kenny Rogers | | 402 | 406 | -4 |
| 2003-07-04 | vs CLE | 85 | W 9-2 | 44-41 | 2 | 21,328 | Rick Reed | Jason Davis | Rick Reed | Jason Davis | | 411 | 408 | 3 |
| 2003-07-05 | vs CLE | 86 | L 2-13 | 44-42 | 2 | 20,273 | Joe Mays | Brian Anderson | Brian Anderson | Joe Mays | | 413 | 421 | -8 |
| 2003-07-06 | vs CLE | 87 | L 3-5 | 44-43 | 2 | 20,549 | Brad Radke | Jason Stanford | David Riske | Eddie Guardado | Danys Baez | 416 | 426 | -10 |
| 2003-07-08 | @ TEX | 88 | L 6-8 | 44-44 | 2 | 17,353 | Kyle Lohse | Tony Mounce | Jay Powell | Kyle Lohse | Ugueth Urbina | 422 | 434 | -12 |
| 2003-07-09 | @ TEX | 89 | L 1-4 | 44-45 | 2 | 20,409 | Kenny Rogers | Joaquin Benoit | Joaquin Benoit | Kenny Rogers | Ugueth Urbina | 423 | 438 | -15 |
| 2003-07-10 | @ TEX | 90 | L 4-9 | 44-46 | 2 | 17,507 | Rick Reed | John Thomson | John Thomson | Rick Reed | | 427 | 447 | -20 |
| 2003-07-11 | @ ANA | 91 | L 0-5 | 44-47 | 2 | 43,442 | Johan Santana | Ramon Ortiz | Ramon Ortiz | Johan Santana | Brendan Donnelly | 427 | 452 | -25 |
| 2003-07-12 | @ ANA | 92 | L 1-6 | 44-48 | 2 | 43,174 | Brad Radke | Jarrod Washburn | Jarrod Washburn | Brad Radke | | 428 | 458 | -30 |
| 2003-07-13 | @ ANA | 93 | L 3-8 | 44-49 | 3 | 38,835 | Kyle Lohse | John Lackey | John Lackey | Kyle Lohse | | 431 | 466 | -35 |
| 2003-07-17 | vs OAK | 94 | W 6-2 | 45-49 | 2 | 20,139 | Rick Reed | Tim Hudson | Rick Reed | Tim Hudson | | 437 | 468 | -31 |
| 2003-07-18 | vs OAK | 95 | W 3-2 | 46-49 | 2 | 21,852 | Johan Santana | Barry Zito | LaTroy Hawkins | Barry Zito | Eddie Guardado | 440 | 470 | -30 |
| 2003-07-19 | vs OAK | 96 | W 9-4 | 47-49 | 2 | 25,392 | Brad Radke | Mark Mulder | Brad Radke | Mark Mulder | | 449 | 474 | -25 |
| 2003-07-20 | vs OAK | 97 | W 6-4 | 48-49 | 2 | 26,799 | Kenny Rogers | Ted Lilly | Kenny Rogers | Ted Lilly | Eddie Guardado | 455 | 478 | -23 |
| 2003-07-21 | vs SEA | 98 | W 5-4 | 49-49 | 2 | 20,306 | Kyle Lohse | Joel Pineiro | Juan Rincon | Arthur Rhodes | Eddie Guardado | 460 | 482 | -22 |
| 2003-07-22 | vs SEA | 99 | L 8-10 | 49-50 | 3 | 22,229 | Rick Reed | Freddy Garcia | Julio Mateo | Joe Mays | Shigetoshi Hasegawa | 468 | 492 | -24 |
| 2003-07-23 | vs KCA | 100 | L 3-8 | 49-51 | 3 | 24,193 | Johan Santana | Jeremy Affeldt | Jeremy Affeldt | Johan Santana | | 471 | 500 | -29 |
| 2003-07-24 | vs KCA | 101 | W 6-2 | 50-51 | 3 | 29,687 | Brad Radke | Darrell May | LaTroy Hawkins | Jason Grimsley | | 477 | 502 | -25 |
| 2003-07-25 | @ CLE | 102 | W 6-5 | 51-51 | 3 | 23,444 | Kenny Rogers | Jake Westbrook | LaTroy Hawkins | Danys Baez | Eddie Guardado | 483 | 507 | -24 |
| 2003-07-26 | @ CLE | 103 | L 2-9 | 51-52 | 3 | 25,077 | Kyle Lohse | Billy Traber | Billy Traber | Kyle Lohse | | 485 | 516 | -31 |
| 2003-07-27 | @ CLE | 104 | L 2-3 | 51-53 | 3 | 24,318 | Rick Reed | Jason Davis | Rafael Betancourt | Juan Rincon | | 487 | 519 | -32 |
| 2003-07-29 | vs BAL | 105 | L 5-7 | 51-54 | 3 | 20,742 | Johan Santana | Rick Helling | Hector Carrasco | LaTroy Hawkins | Jorge Julio | 492 | 526 | -34 |
| 2003-07-30 | vs BAL | 106 | W 5-1 | 52-54 | 3 | 24,694 | Brad Radke | Sidney Ponson | Brad Radke | Sidney Ponson | | 497 | 527 | -30 |
| 2003-07-31 | vs BAL | 107 | W 10-9 | 53-54 | 3 | 20,002 | Kenny Rogers | Jason Johnson | LaTroy Hawkins | Travis Driskill | | 507 | 536 | -29 |
| 2003-08-01 | vs DET | 108 | W 10-4 | 54-54 | 3 | 20,101 | Kyle Lohse | Jeremy Bonderman | Kyle Lohse | Jeremy Bonderman | James Baldwin | 517 | 540 | -23 |
| 2003-08-02 | vs DET | 109 | L 2-9 | 54-55 | 3 | 29,278 | Rick Reed | Mike Maroth | Mike Maroth | Rick Reed | | 519 | 549 | -30 |
| 2003-08-03 | vs DET | 110 | W 7-2 | 55-55 | 3 | 27,613 | Johan Santana | Matt Roney | Johan Santana | Matt Roney | | 526 | 551 | -25 |
| 2003-08-04 | @ BAL | 111 | W 3-2 | 56-55 | 3 | 24,077 | Brad Radke | Damian Moss | Brad Radke | Damian Moss | Eddie Guardado | 529 | 553 | -24 |
| 2003-08-05 | @ BAL | 112 | L 2-3 | 56-56 | 3 | 26,031 | Kenny Rogers | Jason Johnson | Jason Johnson | Kenny Rogers | Jorge Julio | 531 | 556 | -25 |
| 2003-08-06 | @ BAL | 113 | W 7-3 | 57-56 | 3 | 24,392 | Kyle Lohse | Pat Hentgen | Kyle Lohse | Pat Hentgen | | 538 | 559 | -21 |
| 2003-08-07 | @ BAL | 114 | L 3-5 | 57-57 | 3 | 30,258 | Rick Reed | Rodrigo Lopez | Rodrigo Lopez | Rick Reed | Jorge Julio | 541 | 564 | -23 |
| 2003-08-08 | @ DET | 115 | W 4-3 | 58-57 | 3 | 23,740 | Johan Santana | Mike Maroth | Johan Santana | Mike Maroth | Eddie Guardado | 545 | 567 | -22 |
| 2003-08-09 | @ DET | 116 | W 8-4 | 59-57 | 3 | 19,199 | Brad Radke | Matt Roney | Juan Rincon | Chris Mears | | 553 | 571 | -18 |
| 2003-08-10 | @ DET | 117 | W 4-3 | 60-57 | 3 | 19,975 | Kenny Rogers | Nate Cornejo | Kenny Rogers | Nate Cornejo | Eddie Guardado | 557 | 574 | -17 |
| 2003-08-11 | vs CLE | 118 | W 5-3 | 61-57 | 3 | 23,291 | Kyle Lohse | Jake Westbrook | Kyle Lohse | Jake Westbrook | LaTroy Hawkins | 562 | 577 | -15 |
| 2003-08-12 | vs CLE | 119 | L 6-9 | 61-58 | 3 | 25,834 | Joe Mays | Billy Traber | Rafael Betancourt | James Baldwin | | 568 | 586 | -18 |
| 2003-08-13 | vs CLE | 120 | L 0-5 | 61-59 | 3 | 30,082 | Johan Santana | Jason Davis | Terry Mulholland | Juan Rincon | | 568 | 591 | -23 |
| 2003-08-14 | vs CLE | 121 | L 3-8 | 61-60 | 3 | 24,273 | Brad Radke | Brian Anderson | Brian Anderson | Brad Radke | | 571 | 599 | -28 |
| 2003-08-15 | @ KCA | 122 | W 9-2 | 62-60 | 3 | 39,927 | Kenny Rogers | Jimmy Gobble | Kenny Rogers | Jimmy Gobble | | 580 | 601 | -21 |
| 2003-08-16 | @ KCA | 123 | W 14-5 | 63-60 | 3 | 28,994 | Kyle Lohse | Runelvys Hernandez | Kyle Lohse | Runelvys Hernandez | | 594 | 606 | -12 |
| 2003-08-17 | @ KCA | 124 | L 4-5 | 63-61 | 3 | 18,875 | Rick Reed | Darrell May | Darrell May | Rick Reed | Curt Leskanic | 598 | 611 | -13 |
| 2003-08-19 | @ CLE | 125 | W 8-2 | 64-61 | 3 | 21,239 | Johan Santana | Jason Davis | Johan Santana | Jason Davis | | 606 | 613 | -7 |
| 2003-08-20 | @ CLE | 126 | W 4-3 | 65-61 | 3 | 20,197 | Brad Radke | Brian Anderson | Brad Radke | Brian Anderson | Eddie Guardado | 610 | 616 | -6 |
| 2003-08-21 | vs KCA | 127 | W 4-3 | 66-61 | 2 | 30,179 | Kenny Rogers | Paul Abbott | Kenny Rogers | Al Levine | Eddie Guardado | 614 | 619 | -5 |
| 2003-08-22 | vs KCA | 128 | L 2-3 | 66-62 | 3 | 36,101 | Kyle Lohse | Darrell May | Darrell May | Kyle Lohse | Jeremy Affeldt | 616 | 622 | -6 |
| 2003-08-23 | vs KCA | 129 | L 3-4 | 66-63 | 3 | 37,782 | Joe Mays | Jose Lima | D.J. Carrasco | Joe Mays | Mike MacDougal | 619 | 626 | -7 |
| 2003-08-24 | vs KCA | 130 | W 8-1 | 67-63 | 3 | 34,265 | Johan Santana | Kevin Appier | Johan Santana | Graeme Lloyd | | 627 | 627 | 0 |
| 2003-08-26 | @ ANA | 131 | W 3-0 | 68-63 | 3 | 35,415 | Brad Radke | John Lackey | Brad Radke | John Lackey | | 630 | 627 | 3 |
| 2003-08-27 | @ ANA | 132 | L 4-5 | 68-64 | 3 | 36,323 | Kenny Rogers | Aaron Sele | Ben Weber | Juan Rincon | Troy Percival | 634 | 632 | 2 |
| 2003-08-28 | @ ANA | 133 | W 6-1 | 69-64 | 3 | 33,760 | Kyle Lohse | Ramon Ortiz | Kyle Lohse | Ramon Ortiz | | 640 | 633 | 7 |
| 2003-08-29 | @ TEX | 134 | W 8-5 | 70-64 | 3 | 18,118 | Joe Mays | John Thomson | Grant Balfour | John Thomson | Eddie Guardado | 648 | 638 | 10 |
| 2003-08-30 | @ TEX | 135 | W 2-0 | 71-64 | 3 | 30,068 | Johan Santana | Mickey Callaway | Johan Santana | Mickey Callaway | Eddie Guardado | 650 | 638 | 12 |
| 2003-08-31 | @ TEX | 136 | L 10-11 | 71-65 | 3 | 17,213 | Brad Radke | R.A. Dickey | Francisco Cordero | Eddie Guardado | | 660 | 649 | 11 |
| 2003-09-01 | vs ANA | 137 | L 2-10 | 71-66 | 3 | 22,208 | Kenny Rogers | John Lackey | John Lackey | Kenny Rogers | | 662 | 659 | 3 |
| 2003-09-02 | vs ANA | 138 | W 12-6 | 72-66 | 2 | 13,307 | Kyle Lohse | Aaron Sele | Kyle Lohse | Aaron Sele | | 674 | 665 | 9 |
| 2003-09-03 | vs ANA | 139 | W 6-5 | 73-66 | 2 | 11,434 | Grant Balfour | Ramon Ortiz | Eddie Guardado | Troy Percival | | 680 | 670 | 10 |
| 2003-09-05 | vs TEX | 140 | W 10-7 | 74-66 | 2 | 20,701 | Johan Santana | Mickey Callaway | Juan Rincon | Mickey Callaway | Eddie Guardado | 690 | 677 | 13 |
| 2003-09-06 | vs TEX | 141 | W 5-2 | 75-66 | 2 | 27,018 | Brad Radke | R.A. Dickey | Brad Radke | R.A. Dickey | Eddie Guardado | 695 | 679 | 16 |
| 2003-09-07 | vs TEX | 142 | W 5-4 | 76-66 | 2 | 18,941 | Kenny Rogers | Colby Lewis | Rick Reed | Francisco Cordero | | 700 | 683 | 17 |
| 2003-09-08 | @ CHA | 143 | L 2-5 | 76-67 | 2 | 32,807 | Kyle Lohse | Bartolo Colon | Bartolo Colon | Kyle Lohse | | 702 | 688 | 14 |
| 2003-09-09 | @ CHA | 144 | L 6-8 | 76-68 | 2 | 27,623 | Carlos Pulido | Mark Buehrle | Mark Buehrle | Carlos Pulido | Tom Gordon | 708 | 696 | 12 |
| 2003-09-10 | @ CHA | 145 | W 4-1 | 77-68 | 2 | 22,188 | Johan Santana | Jon Garland | Johan Santana | Jon Garland | Eddie Guardado | 712 | 697 | 15 |
| 2003-09-11 | @ CHA | 146 | W 5-2 | 78-68 | 2 | 20,541 | Brad Radke | Esteban Loaiza | Brad Radke | Esteban Loaiza | | 717 | 699 | 18 |
| 2003-09-12 | @ CLE | 147 | L 3-4 | 78-69 | 2 | 20,679 | Kenny Rogers | CC Sabathia | CC Sabathia | Kenny Rogers | David Riske | 720 | 703 | 17 |
| 2003-09-13 | @ CLE | 148 | W 2-0 | 79-69 | 2 | 20,440 | Kyle Lohse | Jason Stanford | Kyle Lohse | Jason Stanford | Eddie Guardado | 722 | 703 | 19 |
| 2003-09-14 | @ CLE | 149 | W 5-3 | 80-69 | 2 | 19,452 | Eric Milton | Cliff Lee | Juan Rincon | Danys Baez | Eddie Guardado | 727 | 706 | 21 |
| 2003-09-15 | @ CLE | 150 | W 13-6 | 81-69 | 1 | 16,967 | Johan Santana | Jason Davis | Johan Santana | Jason Davis | | 740 | 712 | 28 |
| 2003-09-16 | vs CHA | 151 | W 5-2 | 82-69 | 1 | 32,921 | Brad Radke | Esteban Loaiza | Brad Radke | Esteban Loaiza | | 745 | 714 | 31 |
| 2003-09-17 | vs CHA | 152 | W 4-2 | 83-69 | 1 | 40,304 | Kenny Rogers | Jon Garland | Kenny Rogers | Jon Garland | Eddie Guardado | 749 | 716 | 33 |
| 2003-09-18 | vs CHA | 153 | W 5-3 | 84-69 | 1 | 39,948 | Kyle Lohse | Bartolo Colon | Kyle Lohse | Bartolo Colon | Eddie Guardado | 754 | 719 | 35 |
| 2003-09-19 | vs DET | 154 | W 6-2 | 85-69 | 1 | 30,013 | Eric Milton | Jeremy Bonderman | Eric Milton | Jeremy Bonderman | | 760 | 721 | 39 |
| 2003-09-20 | vs DET | 155 | W 7-3 | 86-69 | 1 | 26,903 | Johan Santana | Nate Robertson | Johan Santana | Nate Robertson | | 767 | 724 | 43 |
| 2003-09-21 | vs DET | 156 | W 6-4 | 87-69 | 1 | 33,396 | Brad Radke | Nate Cornejo | Brad Radke | Nate Cornejo | Eddie Guardado | 773 | 728 | 45 |
| 2003-09-23 | vs CLE | 157 | W 4-1 | 88-69 | 1 | 33,650 | Kenny Rogers | Jake Westbrook | Kenny Rogers | Jake Westbrook | Eddie Guardado | 777 | 729 | 48 |
| 2003-09-24 | vs CLE | 158 | W 3-2 | 89-69 | 1 | 32,986 | Kyle Lohse | CC Sabathia | Jesse Orosco | Rafael Betancourt | Eddie Guardado | 780 | 731 | 49 |
| 2003-09-25 | @ DET | 159 | L 4-5 | 89-70 | 1 | 9,296 | Johan Santana | Nate Robertson | Chris Mears | Brad Thomas | | 784 | 736 | 48 |
| 2003-09-26 | @ DET | 160 | W 5-4 | 90-70 | 1 | 16,518 | Eric Milton | Nate Cornejo | Eddie Guardado | Franklyn German | LaTroy Hawkins | 789 | 740 | 49 |
| 2003-09-27 | @ DET | 161 | L 8-9 | 90-71 | 1 | 14,277 | Brad Radke | Gary Knotts | Fernando Rodney | Jesse Orosco | | 797 | 749 | 48 |
| 2003-09-28 | @ DET | 162 | L 4-9 | 90-72 | 1 | 18,959 | Kyle Lohse | Mike Maroth | Mike Maroth | Adam Johnson | | 801 | 758 | 43 |