| 2003-03-31 | vs MIN | 1 | L 1-3 | 0-1 | 5 | 40,427 | Mike Maroth | Brad Radke | Brad Radke | Mike Maroth | Eddie Guardado | 1 | 3 | -2 |
| 2003-04-02 | vs MIN | 2 | L 1-8 | 0-2 | 5 | 21,123 | Jeremy Bonderman | Joe Mays | Joe Mays | Jeremy Bonderman | | 2 | 11 | -9 |
| 2003-04-03 | vs MIN | 3 | L 0-3 | 0-3 | 5 | 8,862 | Adam Bernero | Kyle Lohse | Kyle Lohse | Adam Bernero | Eddie Guardado | 2 | 14 | -12 |
| 2003-04-04 | @ CHA | 4 | L 2-5 | 0-4 | 5 | 40,395 | Nate Cornejo | Esteban Loaiza | Esteban Loaiza | Nate Cornejo | Billy Koch | 4 | 19 | -15 |
| 2003-04-05 | @ CHA | 5 | L 0-7 | 0-5 | 5 | 16,972 | Mike Maroth | Mark Buehrle | Mark Buehrle | Mike Maroth | | 4 | 26 | -22 |
| 2003-04-06 | @ CHA | 6 | L 2-10 | 0-6 | 5 | 14,514 | Gary Knotts | Josh Stewart | Damaso Marte | Franklyn German | | 6 | 36 | -30 |
| 2003-04-09 | vs KCA | 7 | L 6-9 | 0-7 | 5 | 14,286 | Jeremy Bonderman | Jeremy Affeldt | Jeremy Affeldt | Jeremy Bonderman | Mike MacDougal | 12 | 45 | -33 |
| 2003-04-10 | vs KCA | 8 | L 2-4 | 0-8 | 5 | 9,080 | Mike Maroth | Miguel Asencio | Miguel Asencio | Mike Maroth | Mike MacDougal | 14 | 49 | -35 |
| 2003-04-11 | vs CHA | 9 | L 0-5 | 0-9 | 5 | 12,577 | Adam Bernero | Esteban Loaiza | Esteban Loaiza | Adam Bernero | | 14 | 54 | -40 |
| 2003-04-12 | vs CHA | 10 | W 4-3 | 1-9 | 5 | 12,985 | Nate Cornejo | Josh Stewart | Nate Cornejo | Josh Stewart | Matt Anderson | 18 | 57 | -39 |
| 2003-04-13 | vs CHA | 11 | L 2-3 | 1-10 | 5 | 12,808 | Gary Knotts | Bartolo Colon | Bartolo Colon | Gary Knotts | Billy Koch | 20 | 60 | -40 |
| 2003-04-15 | @ MIN | 12 | L 4-6 | 1-11 | 5 | 14,036 | Mike Maroth | Kyle Lohse | Kyle Lohse | Mike Maroth | Eddie Guardado | 24 | 66 | -42 |
| 2003-04-16 | @ MIN | 13 | L 2-4 | 1-12 | 5 | 13,503 | Adam Bernero | Rick Reed | Rick Reed | Adam Bernero | Eddie Guardado | 26 | 70 | -44 |
| 2003-04-17 | @ MIN | 14 | L 0-6 | 1-13 | 5 | 13,015 | Jeremy Bonderman | Kenny Rogers | Kenny Rogers | Jeremy Bonderman | | 26 | 76 | -50 |
| 2003-04-18 | @ KCA | 15 | L 3-4 | 1-14 | 5 | 38,937 | Nate Cornejo | Darrell May | D.J. Carrasco | Matt Anderson | | 29 | 80 | -51 |
| 2003-04-19 | @ KCA | 16 | L 2-9 | 1-15 | 5 | 13,777 | Gary Knotts | Jeremy Affeldt | Albie Lopez | Gary Knotts | | 31 | 89 | -58 |
| 2003-04-20 | @ KCA | 17 | L 3-4 | 1-16 | 5 | 16,203 | Mike Maroth | Miguel Asencio | Mike MacDougal | Mike Maroth | | 34 | 93 | -59 |
| 2003-04-22 | @ OAK | 18 | L 5-6 | 1-17 | 5 | 11,559 | Adam Bernero | Tim Hudson | Ricardo Rincon | Wil Ledezma | | 39 | 99 | -60 |
| 2003-04-23 | @ OAK | 19 | W 4-1 | 2-17 | 5 | 23,558 | Jeremy Bonderman | Barry Zito | Jeremy Bonderman | Barry Zito | Matt Anderson | 43 | 100 | -57 |
| 2003-04-24 | @ OAK | 20 | L 0-2 | 2-18 | 5 | 11,843 | Nate Cornejo | Mark Mulder | Mark Mulder | Nate Cornejo | | 43 | 102 | -59 |
| 2003-04-25 | @ SEA | 21 | L 0-6 | 2-19 | 5 | 33,458 | Mike Maroth | Joel Pineiro | Joel Pineiro | Mike Maroth | | 43 | 108 | -65 |
| 2003-04-26 | @ SEA | 22 | W 6-4 | 3-19 | 5 | 36,258 | Gary Knotts | Ryan Franklin | Jamie Walker | Ryan Franklin | Matt Anderson | 49 | 112 | -63 |
| 2003-04-27 | @ SEA | 23 | L 3-4 | 3-20 | 5 | 39,678 | Adam Bernero | Freddy Garcia | Freddy Garcia | Adam Bernero | Jeff Nelson | 52 | 116 | -64 |
| 2003-04-29 | vs BAL | 24 | L 3-11 | 3-21 | 5 | 10,829 | Jeremy Bonderman | Jason Johnson | Jason Johnson | Jeremy Bonderman | | 55 | 127 | -72 |
| 2003-05-01 | vs BAL | 25 | L 2-5 | 3-23 | 5 | 0 | Nate Cornejo | Rodrigo Lopez | B.J. Ryan | Franklyn German | Jorge Julio | 57 | 132 | -75 |
| 2003-05-01 | vs BAL | 26 | L 4-6 | 3-23 | 5 | 16,177 | Mike Maroth | Omar Daal | Omar Daal | Mike Maroth | Jorge Julio | 61 | 138 | -77 |
| 2003-05-02 | vs TBA | 27 | L 0-2 | 3-24 | 5 | 14,571 | Gary Knotts | Joe Kennedy | Joe Kennedy | Gary Knotts | | 61 | 140 | -79 |
| 2003-05-03 | vs TBA | 28 | L 6-8 | 3-25 | 5 | 13,371 | Adam Bernero | Dewon Brazelton | Al Levine | Wil Ledezma | | 67 | 148 | -81 |
| 2003-05-04 | vs TBA | 29 | W 7-3 | 4-25 | 5 | 12,956 | Jeremy Bonderman | Jorge Sosa | Jeremy Bonderman | Jorge Sosa | Chris Spurling | 74 | 151 | -77 |
| 2003-05-05 | @ BAL | 30 | W 6-1 | 5-25 | 5 | 17,267 | Nate Cornejo | Jason Johnson | Nate Cornejo | Jason Johnson | Steve Sparks | 80 | 152 | -72 |
| 2003-05-06 | @ BAL | 31 | W 7-6 | 6-25 | 5 | 22,906 | Mike Maroth | Pat Hentgen | Franklyn German | Buddy Groom | | 87 | 158 | -71 |
| 2003-05-07 | @ BAL | 32 | W 9-4 | 7-25 | 5 | 22,770 | Gary Knotts | Omar Daal | Gary Knotts | Omar Daal | | 96 | 162 | -66 |
| 2003-05-09 | @ TBA | 33 | L 0-2 | 7-26 | 5 | 8,894 | Adam Bernero | Jim Parque | Jim Parque | Adam Bernero | Lance Carter | 96 | 164 | -68 |
| 2003-05-10 | @ TBA | 34 | L 1-3 | 7-27 | 5 | 12,325 | Jeremy Bonderman | Seth McClung | Seth McClung | Jeremy Bonderman | Lance Carter | 97 | 167 | -70 |
| 2003-05-11 | @ TBA | 35 | W 9-2 | 8-27 | 5 | 9,259 | Nate Cornejo | Jorge Sosa | Nate Cornejo | Jorge Sosa | | 106 | 169 | -63 |
| 2003-05-13 | vs OAK | 36 | L 1-3 | 8-28 | 5 | 12,563 | Mike Maroth | Ted Lilly | Ted Lilly | Mike Maroth | Keith Foulke | 107 | 172 | -65 |
| 2003-05-14 | vs OAK | 37 | W 2-1 | 9-28 | 5 | 11,091 | Gary Knotts | Tim Hudson | Steve Avery | Ricardo Rincon | | 109 | 173 | -64 |
| 2003-05-15 | vs OAK | 38 | L 2-11 | 9-29 | 5 | 10,513 | Adam Bernero | Barry Zito | Barry Zito | Adam Bernero | | 111 | 184 | -73 |
| 2003-05-16 | vs SEA | 39 | L 3-6 | 9-30 | 5 | 17,641 | Jeremy Bonderman | Gil Meche | Gil Meche | Jeremy Bonderman | Kazuhiro Sasaki | 114 | 190 | -76 |
| 2003-05-17 | vs SEA | 40 | L 3-6 | 9-31 | 5 | 23,274 | Nate Cornejo | Jamie Moyer | Jamie Moyer | Nate Cornejo | Kazuhiro Sasaki | 117 | 196 | -79 |
| 2003-05-18 | vs SEA | 41 | L 2-6 | 9-32 | 5 | 16,263 | Mike Maroth | Joel Pineiro | Joel Pineiro | Mike Maroth | | 119 | 202 | -83 |
| 2003-05-19 | @ CLE | 42 | L 9-10 | 9-33 | 5 | 16,492 | Gary Knotts | Jason Davis | Billy Traber | Jamie Walker | David Riske | 128 | 212 | -84 |
| 2003-05-20 | @ CLE | 43 | L 4-6 | 9-34 | 5 | 15,499 | Adam Bernero | Jake Westbrook | David Riske | Matt Roney | | 132 | 218 | -86 |
| 2003-05-21 | @ CLE | 44 | L 0-4 | 9-35 | 5 | 16,534 | Jeremy Bonderman | CC Sabathia | CC Sabathia | Jeremy Bonderman | | 132 | 222 | -90 |
| 2003-05-22 | @ CLE | 45 | W 3-2 | 10-35 | 5 | 18,347 | Nate Cornejo | Jason Bere | Franklyn German | Jason Phillips | Steve Sparks | 135 | 224 | -89 |
| 2003-05-23 | @ CHA | 46 | W 3-2 | 11-35 | 5 | 15,069 | Mike Maroth | Jon Garland | Mike Maroth | Tom Gordon | Chris Spurling | 138 | 226 | -88 |
| 2003-05-24 | @ CHA | 47 | W 1-0 | 12-35 | 5 | 27,535 | Gary Knotts | Esteban Loaiza | Gary Knotts | Esteban Loaiza | Franklyn German | 139 | 226 | -87 |
| 2003-05-25 | @ CHA | 48 | L 5-8 | 12-36 | 5 | 21,398 | Adam Bernero | Dan Wright | Gary Glover | Steve Sparks | | 144 | 234 | -90 |
| 2003-05-26 | vs CLE | 49 | W 6-5 | 13-36 | 5 | 17,619 | Jeremy Bonderman | Jake Westbrook | Steve Avery | Jason Boyd | Franklyn German | 150 | 239 | -89 |
| 2003-05-27 | vs CLE | 50 | L 2-5 | 13-37 | 5 | 10,844 | Nate Cornejo | Jason Bere | Dan Miceli | Jamie Walker | Danys Baez | 152 | 244 | -92 |
| 2003-05-28 | vs CLE | 51 | L 2-8 | 13-38 | 5 | 17,388 | Mike Maroth | Ricardo Rodriguez | Ricardo Rodriguez | Mike Maroth | | 154 | 252 | -98 |
| 2003-05-30 | vs NYA | 52 | L 0-6 | 13-39 | 5 | 28,003 | Gary Knotts | Jose Contreras | Jose Contreras | Gary Knotts | | 154 | 258 | -104 |
| 2003-05-31 | vs NYA | 53 | W 4-2 | 14-39 | 5 | 24,959 | Adam Bernero | Jeff Weaver | Adam Bernero | Jeff Weaver | Franklyn German | 158 | 260 | -102 |
| 2003-06-01 | vs NYA | 54 | L 9-10 | 14-40 | 5 | 44,095 | Jeremy Bonderman | Roger Clemens | David Wells | Steve Sparks | Juan Acevedo | 167 | 270 | -103 |
| 2003-06-03 | @ SDN | 55 | W 3-2 | 15-40 | 5 | 15,521 | Nate Cornejo | Brian Lawrence | Jamie Walker | Brian Lawrence | Franklyn German | 170 | 272 | -102 |
| 2003-06-04 | @ SDN | 56 | W 5-3 | 16-40 | 5 | 13,227 | Gary Knotts | Brian Tollberg | Wil Ledezma | Luther Hackman | Franklyn German | 175 | 275 | -100 |
| 2003-06-05 | @ SDN | 57 | L 1-5 | 16-41 | 5 | 14,710 | Adam Bernero | Adam Eaton | Adam Eaton | Adam Bernero | | 176 | 280 | -104 |
| 2003-06-06 | @ SFN | 58 | L 3-5 | 16-42 | 5 | 41,554 | Jeremy Bonderman | Kirk Rueter | Kirk Rueter | Jeremy Bonderman | Tim Worrell | 179 | 285 | -106 |
| 2003-06-07 | @ SFN | 59 | L 5-7 | 16-43 | 5 | 40,060 | Mike Maroth | Jason Schmidt | Jason Schmidt | Mike Maroth | | 184 | 292 | -108 |
| 2003-06-08 | @ SFN | 60 | L 6-7 | 16-44 | 5 | 41,177 | Nate Cornejo | Damian Moss | Joe Nathan | Franklyn German | Tim Worrell | 190 | 299 | -109 |
| 2003-06-10 | vs LAN | 61 | L 1-3 | 16-45 | 5 | 13,419 | Gary Knotts | Hideo Nomo | Paul Shuey | Steve Sparks | Eric Gagne | 191 | 302 | -111 |
| 2003-06-11 | vs LAN | 62 | L 1-3 | 16-46 | 5 | 13,716 | Adam Bernero | Kevin Brown | Kevin Brown | Adam Bernero | Eric Gagne | 192 | 305 | -113 |
| 2003-06-12 | vs LAN | 63 | L 2-3 | 16-47 | 5 | 13,644 | Jeremy Bonderman | Kazuhisa Ishii | Kazuhisa Ishii | Jeremy Bonderman | Eric Gagne | 194 | 308 | -114 |
| 2003-06-13 | vs COL | 64 | L 2-7 | 16-48 | 5 | 19,212 | Nate Cornejo | Shawn Chacon | Shawn Chacon | Nate Cornejo | | 196 | 315 | -119 |
| 2003-06-14 | vs COL | 65 | W 9-7 | 17-48 | 5 | 19,260 | Mike Maroth | Scott Elarton | Wil Ledezma | Scott Elarton | Chris Spurling | 205 | 322 | -117 |
| 2003-06-15 | vs COL | 66 | L 4-5 | 17-49 | 5 | 19,323 | Gary Knotts | Jason Jennings | Jason Jennings | Gary Knotts | Jose Jimenez | 209 | 327 | -118 |
| 2003-06-17 | vs CLE | 67 | L 4-7 | 17-50 | 5 | 13,908 | Adam Bernero | CC Sabathia | CC Sabathia | Adam Bernero | Danys Baez | 213 | 334 | -121 |
| 2003-06-18 | vs CLE | 68 | L 1-4 | 17-51 | 5 | 16,278 | Jeremy Bonderman | Jason Davis | Jason Davis | Jeremy Bonderman | | 214 | 338 | -124 |
| 2003-06-19 | vs CLE | 69 | L 3-10 | 17-52 | 5 | 19,098 | Nate Cornejo | Brian Anderson | Brian Anderson | Nate Cornejo | | 217 | 348 | -131 |
| 2003-06-20 | @ COL | 70 | W 7-5 | 18-52 | 5 | 29,603 | Mike Maroth | Scott Elarton | Mike Maroth | Scott Elarton | | 224 | 353 | -129 |
| 2003-06-21 | @ COL | 71 | L 6-9 | 18-53 | 5 | 35,660 | Matt Roney | Jason Jennings | Jason Jennings | Steve Sparks | | 230 | 362 | -132 |
| 2003-06-22 | @ COL | 72 | L 3-5 | 18-54 | 5 | 34,723 | Adam Bernero | Denny Neagle | Denny Neagle | Adam Bernero | Jose Jimenez | 233 | 367 | -134 |
| 2003-06-23 | @ BOS | 73 | L 1-3 | 18-55 | 5 | 33,814 | Jeremy Bonderman | Tim Wakefield | Tim Wakefield | Jeremy Bonderman | Mike Timlin | 234 | 370 | -136 |
| 2003-06-24 | @ BOS | 74 | L 1-10 | 18-56 | 5 | 33,848 | Nate Cornejo | Derek Lowe | Derek Lowe | Nate Cornejo | | 235 | 380 | -145 |
| 2003-06-25 | @ BOS | 75 | L 2-11 | 18-57 | 5 | 33,587 | Mike Maroth | John Burkett | John Burkett | Mike Maroth | | 237 | 391 | -154 |
| 2003-06-26 | @ BOS | 76 | L 4-6 | 18-58 | 5 | 34,415 | Matt Roney | Pedro Martinez | Pedro Martinez | Matt Roney | Brandon Lyon | 241 | 397 | -156 |
| 2003-06-27 | vs ARI | 77 | L 3-8 | 18-59 | 5 | 27,682 | Adam Bernero | John Patterson | Steve Randolph | Adam Bernero | | 244 | 405 | -161 |
| 2003-06-28 | vs ARI | 78 | L 0-7 | 18-60 | 5 | 20,804 | Jeremy Bonderman | Brandon Webb | Brandon Webb | Jeremy Bonderman | | 244 | 412 | -168 |
| 2003-06-29 | vs ARI | 79 | L 3-5 | 18-61 | 5 | 18,989 | Nate Cornejo | Miguel Batista | Eddie Oropesa | Chris Spurling | Jose Valverde | 247 | 417 | -170 |
| 2003-06-30 | vs TOR | 80 | W 6-2 | 19-61 | 5 | 13,353 | Mike Maroth | Cory Lidle | Mike Maroth | Cory Lidle | | 253 | 419 | -166 |
| 2003-07-01 | vs TOR | 81 | W 5-0 | 20-61 | 5 | 15,448 | Matt Roney | Mark Hendrickson | Matt Roney | Mark Hendrickson | Jamie Walker | 258 | 419 | -161 |
| 2003-07-02 | vs TOR | 82 | L 2-8 | 20-62 | 5 | 16,052 | Adam Bernero | Roy Halladay | Roy Halladay | Adam Bernero | | 260 | 427 | -167 |
| 2003-07-03 | @ KCA | 83 | L 2-3 | 20-63 | 5 | 12,978 | Jeremy Bonderman | Jeremy Affeldt | Jeremy Affeldt | Jeremy Bonderman | Mike MacDougal | 262 | 430 | -168 |
| 2003-07-04 | @ KCA | 84 | L 8-9 | 20-64 | 5 | 39,920 | Nate Cornejo | Chris George | Nate Field | Nate Cornejo | Mike MacDougal | 270 | 439 | -169 |
| 2003-07-05 | @ KCA | 85 | W 9-5 | 21-64 | 5 | 19,030 | Mike Maroth | Brad Voyles | Mike Maroth | Brad Voyles | Jamie Walker | 279 | 444 | -165 |
| 2003-07-06 | @ KCA | 86 | L 3-5 | 21-65 | 5 | 12,844 | Matt Roney | Jose Lima | Jose Lima | Matt Roney | Mike MacDougal | 282 | 449 | -167 |
| 2003-07-08 | vs CHA | 87 | W 2-1 | 22-65 | 5 | 13,643 | Wil Ledezma | Jon Garland | Chris Spurling | Jon Garland | Chris Mears | 284 | 450 | -166 |
| 2003-07-09 | vs CHA | 88 | W 4-2 | 23-65 | 5 | 12,869 | Jeremy Bonderman | Bartolo Colon | Jeremy Bonderman | Bartolo Colon | Chris Mears | 288 | 452 | -164 |
| 2003-07-10 | vs CHA | 89 | W 1-0 | 24-65 | 5 | 18,206 | Nate Cornejo | Esteban Loaiza | Nate Cornejo | Esteban Loaiza | Chris Mears | 289 | 452 | -163 |
| 2003-07-11 | vs BOS | 90 | L 3-5 | 24-66 | 5 | 26,538 | Mike Maroth | John Burkett | John Burkett | Mike Maroth | Byung-Hyun Kim | 292 | 457 | -165 |
| 2003-07-12 | vs BOS | 91 | L 2-4 | 24-67 | 5 | 23,206 | Matt Roney | Pedro Martinez | Todd Jones | Fernando Rodney | Byung-Hyun Kim | 294 | 461 | -167 |
| 2003-07-13 | vs BOS | 92 | W 3-0 | 25-67 | 5 | 23,829 | Wil Ledezma | Tim Wakefield | Wil Ledezma | Tim Wakefield | Chris Mears | 297 | 461 | -164 |
| 2003-07-17 | @ CHA | 93 | W 10-9 | 26-67 | 5 | 17,060 | Mike Maroth | Bartolo Colon | Mike Maroth | Bartolo Colon | | 307 | 470 | -163 |
| 2003-07-18 | @ CHA | 94 | L 5-7 | 26-68 | 5 | 18,868 | Matt Roney | Mark Buehrle | Mark Buehrle | Matt Roney | Tom Gordon | 312 | 477 | -165 |
| 2003-07-19 | @ CHA | 95 | L 2-6 | 26-69 | 5 | 32,245 | Nate Cornejo | Jon Garland | Jon Garland | Nate Cornejo | Damaso Marte | 314 | 483 | -169 |
| 2003-07-20 | @ CHA | 96 | L 1-10 | 26-70 | 5 | 20,631 | Wil Ledezma | Esteban Loaiza | Esteban Loaiza | Wil Ledezma | | 315 | 493 | -178 |
| 2003-07-21 | @ BOS | 97 | L 5-14 | 26-71 | 5 | 33,823 | Jeremy Bonderman | John Burkett | John Burkett | Jeremy Bonderman | Casey Fossum | 320 | 507 | -187 |
| 2003-07-22 | @ BOS | 98 | L 4-7 | 26-72 | 5 | 33,570 | Mike Maroth | Derek Lowe | Derek Lowe | Mike Maroth | | 324 | 514 | -190 |
| 2003-07-23 | @ CLE | 99 | L 1-4 | 26-73 | 5 | 21,202 | Matt Roney | Brian Anderson | Brian Anderson | Matt Roney | Danys Baez | 325 | 518 | -193 |
| 2003-07-24 | @ CLE | 100 | W 7-4 | 27-73 | 5 | 20,857 | Nate Cornejo | CC Sabathia | Nate Cornejo | CC Sabathia | Chris Mears | 332 | 522 | -190 |
| 2003-07-25 | vs KCA | 101 | L 3-8 | 27-74 | 5 | 29,697 | Wil Ledezma | Runelvys Hernandez | Runelvys Hernandez | Wil Ledezma | | 335 | 530 | -195 |
| 2003-07-26 | vs KCA | 102 | W 5-1 | 28-74 | 5 | 24,664 | Jeremy Bonderman | Kyle Snyder | Jeremy Bonderman | Kyle Snyder | | 340 | 531 | -191 |
| 2003-07-27 | vs KCA | 103 | L 1-5 | 28-75 | 5 | 35,326 | Mike Maroth | Jose Lima | Jose Lima | Mike Maroth | | 341 | 536 | -195 |
| 2003-07-29 | @ SEA | 104 | L 5-11 | 28-76 | 5 | 30,732 | Matt Roney | Gil Meche | Gil Meche | Matt Roney | | 346 | 547 | -201 |
| 2003-07-30 | @ SEA | 105 | L 3-13 | 28-77 | 5 | 35,800 | Nate Cornejo | Jamie Moyer | Jamie Moyer | Nate Cornejo | | 349 | 560 | -211 |
| 2003-07-31 | @ SEA | 106 | L 0-4 | 28-78 | 5 | 43,596 | Wil Ledezma | Joel Pineiro | Joel Pineiro | Wil Ledezma | | 349 | 564 | -215 |
| 2003-08-01 | @ MIN | 107 | L 4-10 | 28-79 | 5 | 20,101 | Jeremy Bonderman | Kyle Lohse | Kyle Lohse | Jeremy Bonderman | James Baldwin | 353 | 574 | -221 |
| 2003-08-02 | @ MIN | 108 | W 9-2 | 29-79 | 5 | 29,278 | Mike Maroth | Rick Reed | Mike Maroth | Rick Reed | | 362 | 576 | -214 |
| 2003-08-03 | @ MIN | 109 | L 2-7 | 29-80 | 5 | 27,613 | Matt Roney | Johan Santana | Johan Santana | Matt Roney | | 364 | 583 | -219 |
| 2003-08-05 | vs OAK | 110 | L 2-7 | 29-81 | 5 | 13,263 | Nate Cornejo | Rich Harden | Rich Harden | Nate Cornejo | | 366 | 590 | -224 |
| 2003-08-06 | vs OAK | 111 | L 3-9 | 29-82 | 5 | 16,545 | Wil Ledezma | Tim Hudson | Tim Hudson | Wil Ledezma | | 369 | 599 | -230 |
| 2003-08-07 | vs OAK | 112 | W 3-2 | 30-82 | 5 | 19,664 | Jeremy Bonderman | Barry Zito | Jeremy Bonderman | Barry Zito | Danny Patterson | 372 | 601 | -229 |
| 2003-08-08 | vs MIN | 113 | L 3-4 | 30-83 | 5 | 23,740 | Mike Maroth | Johan Santana | Johan Santana | Mike Maroth | Eddie Guardado | 375 | 605 | -230 |
| 2003-08-09 | vs MIN | 114 | L 4-8 | 30-84 | 5 | 19,199 | Matt Roney | Brad Radke | Juan Rincon | Chris Mears | | 379 | 613 | -234 |
| 2003-08-10 | vs MIN | 115 | L 3-4 | 30-85 | 5 | 19,975 | Nate Cornejo | Kenny Rogers | Kenny Rogers | Nate Cornejo | Eddie Guardado | 382 | 617 | -235 |
| 2003-08-11 | @ TEX | 116 | L 3-9 | 30-86 | 5 | 27,674 | Wil Ledezma | John Thomson | Joaquin Benoit | Steve Sparks | | 385 | 626 | -241 |
| 2003-08-12 | @ TEX | 117 | W 7-4 | 31-86 | 5 | 17,524 | Jeremy Bonderman | Juan Dominguez | Jeremy Bonderman | Juan Dominguez | Danny Patterson | 392 | 630 | -238 |
| 2003-08-13 | @ TEX | 118 | L 3-7 | 31-87 | 5 | 17,491 | Mike Maroth | R.A. Dickey | R.A. Dickey | Mike Maroth | Francisco Cordero | 395 | 637 | -242 |
| 2003-08-14 | @ TEX | 119 | L 3-6 | 31-88 | 5 | 17,019 | Matt Roney | John Thomson | John Thomson | Matt Roney | Francisco Cordero | 398 | 643 | -245 |
| 2003-08-15 | @ ANA | 120 | L 1-3 | 31-89 | 5 | 43,174 | Nate Cornejo | John Lackey | John Lackey | Nate Cornejo | Troy Percival | 399 | 646 | -247 |
| 2003-08-16 | @ ANA | 121 | L 7-11 | 31-90 | 5 | 42,337 | Wil Ledezma | Aaron Sele | Gary Glover | Wil Ledezma | | 406 | 657 | -251 |
| 2003-08-17 | @ ANA | 122 | L 6-11 | 31-91 | 5 | 40,745 | Jeremy Bonderman | Ramon Ortiz | Ramon Ortiz | Jeremy Bonderman | | 412 | 668 | -256 |
| 2003-08-18 | vs TEX | 123 | L 2-4 | 31-92 | 5 | 11,698 | Nate Robertson | Ismael Valdez | Ron Mahay | Steve Sparks | R.A. Dickey | 414 | 672 | -258 |
| 2003-08-19 | vs TEX | 124 | L 4-5 | 31-93 | 5 | 13,501 | Mike Maroth | John Thomson | John Thomson | Mike Maroth | Brian Shouse | 418 | 677 | -259 |
| 2003-08-20 | vs TEX | 125 | L 0-6 | 31-94 | 5 | 13,788 | Nate Cornejo | R.A. Dickey | R.A. Dickey | Nate Cornejo | | 418 | 683 | -265 |
| 2003-08-21 | vs ANA | 126 | L 7-10 | 31-95 | 5 | 12,236 | Shane Loux | Aaron Sele | Aaron Sele | Matt Roney | | 425 | 693 | -268 |
| 2003-08-22 | vs ANA | 127 | L 5-6 | 31-96 | 5 | 21,955 | Jeremy Bonderman | Ramon Ortiz | Ramon Ortiz | Jeremy Bonderman | Troy Percival | 430 | 699 | -269 |
| 2003-08-23 | vs ANA | 128 | L 8-14 | 31-97 | 5 | 26,463 | Nate Robertson | Jarrod Washburn | Brendan Donnelly | Chris Spurling | | 438 | 713 | -275 |
| 2003-08-24 | vs ANA | 129 | W 10-9 | 32-97 | 5 | 17,382 | Mike Maroth | Scot Shields | Jamie Walker | Troy Percival | | 448 | 722 | -274 |
| 2003-08-26 | @ CLE | 130 | W 5-4 | 33-97 | 5 | 16,972 | Nate Cornejo | Billy Traber | Nate Cornejo | Billy Traber | Jamie Walker | 453 | 726 | -273 |
| 2003-08-27 | @ CLE | 131 | L 7-9 | 33-98 | 5 | 16,457 | Shane Loux | Terry Mulholland | Jack Cressend | Chris Spurling | David Riske | 460 | 735 | -275 |
| 2003-08-28 | @ CLE | 132 | L 3-8 | 33-99 | 5 | 16,282 | Jeremy Bonderman | Cliff Lee | Cliff Lee | Jeremy Bonderman | | 463 | 743 | -280 |
| 2003-08-29 | vs CHA | 133 | W 8-4 | 34-99 | 5 | 15,828 | Nate Robertson | Mark Buehrle | Nate Robertson | Mark Buehrle | | 471 | 747 | -276 |
| 2003-08-30 | vs CHA | 134 | L 2-5 | 34-100 | 5 | 15,786 | Mike Maroth | Jon Garland | Jon Garland | Mike Maroth | | 473 | 752 | -279 |
| 2003-08-31 | vs CHA | 135 | L 1-6 | 34-101 | 5 | 15,873 | Nate Cornejo | Esteban Loaiza | Esteban Loaiza | Nate Cornejo | | 474 | 758 | -284 |
| 2003-09-01 | vs CLE | 136 | L 4-7 | 34-102 | 5 | 10,986 | Chris Mears | Jason Stanford | Jose Santiago | Jamie Walker | David Riske | 478 | 765 | -287 |
| 2003-09-02 | vs CLE | 137 | W 8-6 | 35-102 | 5 | 9,318 | Jeremy Bonderman | Cliff Lee | Brian Schmack | Chad Durbin | Fernando Rodney | 486 | 771 | -285 |
| 2003-09-03 | vs CLE | 138 | W 6-5 | 36-102 | 5 | 10,234 | Nate Robertson | CC Sabathia | Jamie Walker | Jose Santiago | | 492 | 776 | -284 |
| 2003-09-04 | vs CLE | 139 | W 2-1 | 37-102 | 5 | 11,371 | Gary Knotts | Jake Westbrook | Gary Knotts | Jake Westbrook | Danny Patterson | 494 | 777 | -283 |
| 2003-09-05 | @ TOR | 140 | L 6-8 | 37-103 | 5 | 14,455 | Mike Maroth | Mark Hendrickson | Tanyon Sturtze | Mike Maroth | Aquilino Lopez | 500 | 785 | -285 |
| 2003-09-06 | @ TOR | 141 | L 0-1 | 37-104 | 5 | 18,261 | Nate Cornejo | Roy Halladay | Roy Halladay | Fernando Rodney | | 500 | 786 | -286 |
| 2003-09-07 | @ TOR | 142 | L 0-8 | 37-105 | 5 | 16,617 | Chris Mears | Josh Towers | Josh Towers | Chris Mears | | 500 | 794 | -294 |
| 2003-09-09 | @ NYA | 143 | L 2-4 | 37-106 | 5 | 31,826 | Nate Robertson | Jose Contreras | Gabe White | Fernando Rodney | Mariano Rivera | 502 | 798 | -296 |
| 2003-09-10 | @ NYA | 144 | L 5-15 | 37-107 | 5 | 34,000 | Gary Knotts | Andy Pettitte | Andy Pettitte | Gary Knotts | | 507 | 813 | -306 |
| 2003-09-11 | @ NYA | 145 | L 2-5 | 37-108 | 5 | 31,915 | Nate Cornejo | Roger Clemens | Roger Clemens | Nate Cornejo | Mariano Rivera | 509 | 818 | -309 |
| 2003-09-12 | vs KCA | 146 | W 3-0 | 38-108 | 5 | 18,042 | Mike Maroth | Paul Abbott | Mike Maroth | Paul Abbott | Fernando Rodney | 512 | 818 | -306 |
| 2003-09-13 | vs KCA | 147 | L 0-7 | 38-109 | 5 | 15,966 | Chris Mears | Jamey Wright | Jamey Wright | Chris Mears | | 512 | 825 | -313 |
| 2003-09-14 | vs KCA | 148 | L 2-7 | 38-110 | 5 | 13,579 | Nate Robertson | Jimmy Gobble | Jimmy Gobble | Nate Robertson | | 514 | 832 | -318 |
| 2003-09-15 | vs KCA | 149 | L 4-10 | 38-111 | 5 | 9,342 | Gary Knotts | Brian Anderson | Brian Anderson | Gary Knotts | | 518 | 842 | -324 |
| 2003-09-16 | vs TOR | 150 | L 6-9 | 38-112 | 5 | 9,801 | Nate Cornejo | Pete Walker | Jason Kershner | Nate Cornejo | | 524 | 851 | -327 |
| 2003-09-17 | vs TOR | 151 | L 0-6 | 38-113 | 5 | 11,240 | Shane Loux | Roy Halladay | Roy Halladay | Shane Loux | | 524 | 857 | -333 |
| 2003-09-18 | vs TOR | 152 | L 6-10 | 38-114 | 5 | 9,951 | Mike Maroth | Josh Towers | Josh Towers | Mike Maroth | | 530 | 867 | -337 |
| 2003-09-19 | @ MIN | 153 | L 2-6 | 38-115 | 5 | 30,013 | Jeremy Bonderman | Eric Milton | Eric Milton | Jeremy Bonderman | | 532 | 873 | -341 |
| 2003-09-20 | @ MIN | 154 | L 3-7 | 38-116 | 5 | 26,903 | Nate Robertson | Johan Santana | Johan Santana | Nate Robertson | | 535 | 880 | -345 |
| 2003-09-21 | @ MIN | 155 | L 4-6 | 38-117 | 5 | 33,396 | Nate Cornejo | Brad Radke | Brad Radke | Nate Cornejo | Eddie Guardado | 539 | 886 | -347 |
| 2003-09-22 | @ KCA | 156 | L 6-12 | 38-118 | 5 | 10,574 | Gary Knotts | Paul Abbott | Jeremy Affeldt | Gary Knotts | | 545 | 898 | -353 |
| 2003-09-23 | @ KCA | 157 | W 15-6 | 39-118 | 5 | 11,180 | Mike Maroth | Jose Lima | Mike Maroth | Jose Lima | | 560 | 904 | -344 |
| 2003-09-24 | @ KCA | 158 | W 4-3 | 40-118 | 5 | 10,758 | Shane Loux | Jimmy Gobble | Shane Loux | Jimmy Gobble | Fernando Rodney | 564 | 907 | -343 |
| 2003-09-25 | vs MIN | 159 | W 5-4 | 41-118 | 5 | 9,296 | Nate Robertson | Johan Santana | Chris Mears | Brad Thomas | | 569 | 911 | -342 |
| 2003-09-26 | vs MIN | 160 | L 4-5 | 41-119 | 5 | 16,518 | Nate Cornejo | Eric Milton | Eddie Guardado | Franklyn German | LaTroy Hawkins | 573 | 916 | -343 |
| 2003-09-27 | vs MIN | 161 | W 9-8 | 42-119 | 5 | 14,277 | Gary Knotts | Brad Radke | Fernando Rodney | Jesse Orosco | | 582 | 924 | -342 |
| 2003-09-28 | vs MIN | 162 | W 9-4 | 43-119 | 5 | 18,959 | Mike Maroth | Kyle Lohse | Mike Maroth | Adam Johnson | | 591 | 928 | -337 |