| 2003-03-30 | vs TEX | 1 | L 3-6 | 0-1 | 2 | 43,525 | John Lackey | Ismael Valdez | Ismael Valdez | John Lackey | Ugueth Urbina | 3 | 6 | -3 |
| 2003-04-01 | vs TEX | 2 | W 10-0 | 1-1 | 2 | 43,267 | Mickey Callaway | Chan Ho Park | Mickey Callaway | Chan Ho Park | | 13 | 6 | 7 |
| 2003-04-02 | vs TEX | 3 | W 11-5 | 2-1 | 2 | 25,821 | Ramon Ortiz | John Thomson | Ramon Ortiz | John Thomson | | 24 | 11 | 13 |
| 2003-04-04 | @ OAK | 4 | L 3-7 | 2-2 | 2 | 18,138 | Kevin Appier | Ted Lilly | Ted Lilly | Kevin Appier | Chad Bradford | 27 | 18 | 9 |
| 2003-04-05 | @ OAK | 5 | L 2-4 | 2-3 | 2 | 23,436 | Jarrod Washburn | John Halama | John Halama | Jarrod Washburn | Keith Foulke | 29 | 22 | 7 |
| 2003-04-06 | @ OAK | 6 | L 6-7 | 2-4 | 3 | 30,140 | John Lackey | Tim Hudson | Chad Bradford | Francisco Rodriguez | Keith Foulke | 35 | 29 | 6 |
| 2003-04-08 | @ SEA | 7 | L 0-5 | 2-5 | 3 | 45,931 | Ramon Ortiz | Jamie Moyer | Jamie Moyer | Ramon Ortiz | | 35 | 34 | 1 |
| 2003-04-09 | @ SEA | 8 | W 5-1 | 3-5 | 3 | 35,492 | Kevin Appier | Joel Pineiro | Kevin Appier | Joel Pineiro | | 40 | 35 | 5 |
| 2003-04-10 | @ SEA | 9 | W 3-0 | 4-5 | 2 | 32,746 | Jarrod Washburn | Ryan Franklin | Jarrod Washburn | Ryan Franklin | Troy Percival | 43 | 35 | 8 |
| 2003-04-11 | vs OAK | 10 | W 9-5 | 5-5 | 2 | 43,707 | John Lackey | Tim Hudson | John Lackey | Tim Hudson | Francisco Rodriguez | 52 | 40 | 12 |
| 2003-04-12 | vs OAK | 11 | W 9-4 | 6-5 | 2 | 43,449 | Mickey Callaway | John Halama | Ben Weber | John Halama | | 61 | 44 | 17 |
| 2003-04-13 | vs OAK | 12 | W 8-2 | 7-5 | 1 | 38,149 | Ramon Ortiz | Barry Zito | Ramon Ortiz | Barry Zito | Scot Shields | 69 | 46 | 23 |
| 2003-04-14 | @ TEX | 13 | L 0-4 | 7-6 | 1 | 24,296 | Kevin Appier | Ismael Valdez | Ismael Valdez | Kevin Appier | | 69 | 50 | 19 |
| 2003-04-15 | @ TEX | 14 | L 4-5 | 7-7 | 2 | 18,152 | Jarrod Washburn | Colby Lewis | Colby Lewis | Jarrod Washburn | Ugueth Urbina | 73 | 55 | 18 |
| 2003-04-16 | @ TEX | 15 | W 9-8 | 8-7 | 1 | 19,014 | John Lackey | Chan Ho Park | Francisco Rodriguez | Francisco Cordero | Troy Percival | 82 | 63 | 19 |
| 2003-04-17 | @ TEX | 16 | L 7-9 | 8-8 | 2 | 18,492 | Mickey Callaway | Ryan Drese | Ryan Drese | Mickey Callaway | Ugueth Urbina | 89 | 72 | 17 |
| 2003-04-18 | vs SEA | 17 | L 2-8 | 8-9 | 3 | 34,658 | Ramon Ortiz | Jamie Moyer | Jamie Moyer | Ramon Ortiz | | 91 | 80 | 11 |
| 2003-04-19 | vs SEA | 18 | W 7-6 | 9-9 | 3 | 43,536 | Kevin Appier | Joel Pineiro | Francisco Rodriguez | Kazuhiro Sasaki | | 98 | 86 | 12 |
| 2003-04-20 | vs SEA | 19 | L 6-7 | 9-10 | 3 | 28,942 | Jarrod Washburn | Ryan Franklin | Shigetoshi Hasegawa | Troy Percival | Kazuhiro Sasaki | 104 | 93 | 11 |
| 2003-04-22 | vs NYA | 20 | L 3-8 | 9-11 | 3 | 38,343 | John Lackey | Jeff Weaver | Jeff Weaver | John Lackey | | 107 | 101 | 6 |
| 2003-04-23 | vs NYA | 21 | L 2-9 | 9-12 | 3 | 38,340 | Mickey Callaway | Roger Clemens | Roger Clemens | Mickey Callaway | | 109 | 110 | -1 |
| 2003-04-24 | vs NYA | 22 | W 6-2 | 10-12 | 3 | 39,169 | Ramon Ortiz | Andy Pettitte | Ramon Ortiz | Andy Pettitte | | 115 | 112 | 3 |
| 2003-04-25 | vs BOS | 23 | L 2-5 | 10-13 | 3 | 37,203 | Jarrod Washburn | Casey Fossum | Casey Fossum | Jarrod Washburn | Chad Fox | 117 | 117 | 0 |
| 2003-04-26 | vs BOS | 24 | W 3-1 | 11-13 | 3 | 43,514 | Scot Shields | John Burkett | Scot Shields | John Burkett | Troy Percival | 120 | 118 | 2 |
| 2003-04-27 | vs BOS | 25 | L 4-6 | 11-14 | 3 | 43,690 | John Lackey | Pedro Martinez | Ramiro Mendoza | Mickey Callaway | Jason Shiell | 124 | 124 | 0 |
| 2003-04-29 | @ CLE | 26 | W 10-1 | 12-14 | 3 | 16,667 | Ramon Ortiz | Ricardo Rodriguez | Ramon Ortiz | Ricardo Rodriguez | | 134 | 125 | 9 |
| 2003-04-30 | @ CLE | 27 | W 6-2 | 13-14 | 3 | 15,761 | Jarrod Washburn | Brian Anderson | Jarrod Washburn | Brian Anderson | | 140 | 127 | 13 |
| 2003-05-02 | @ TOR | 28 | L 1-3 | 13-15 | 3 | 17,799 | John Lackey | Cory Lidle | Cory Lidle | John Lackey | | 141 | 130 | 11 |
| 2003-05-03 | @ TOR | 29 | L 1-7 | 13-16 | 4 | 21,007 | Scot Shields | Doug Davis | Doug Davis | Scot Shields | | 142 | 137 | 5 |
| 2003-05-04 | @ TOR | 30 | L 2-8 | 13-17 | 4 | 21,513 | Ramon Ortiz | Mark Hendrickson | Mark Hendrickson | Ramon Ortiz | Kelvim Escobar | 144 | 145 | -1 |
| 2003-05-06 | vs CLE | 31 | W 6-1 | 14-17 | 3 | 25,043 | Jarrod Washburn | Ricardo Rodriguez | Jarrod Washburn | Ricardo Rodriguez | | 150 | 146 | 4 |
| 2003-05-07 | vs CLE | 32 | W 6-5 | 15-17 | 3 | 24,063 | John Lackey | Brian Anderson | Scot Shields | Dave Elder | Troy Percival | 156 | 151 | 5 |
| 2003-05-08 | vs CLE | 33 | W 7-1 | 16-17 | 3 | 27,957 | Kevin Appier | Jason Davis | Kevin Appier | Jason Davis | | 163 | 152 | 11 |
| 2003-05-09 | vs TOR | 34 | W 6-1 | 17-17 | 3 | 42,820 | Aaron Sele | Doug Davis | Aaron Sele | Doug Davis | | 169 | 153 | 16 |
| 2003-05-10 | vs TOR | 35 | L 4-7 | 17-18 | 3 | 43,661 | Ramon Ortiz | Mark Hendrickson | Mark Hendrickson | Ramon Ortiz | | 173 | 160 | 13 |
| 2003-05-11 | vs TOR | 36 | L 2-4 | 17-19 | 3 | 32,129 | Jarrod Washburn | Roy Halladay | Roy Halladay | Jarrod Washburn | Cliff Politte | 175 | 164 | 11 |
| 2003-05-13 | @ NYA | 37 | W 10-3 | 18-19 | 3 | 37,750 | John Lackey | Mike Mussina | John Lackey | Mike Mussina | | 185 | 167 | 18 |
| 2003-05-14 | @ NYA | 38 | W 5-3 | 19-19 | 3 | 33,647 | Kevin Appier | David Wells | Francisco Rodriguez | David Wells | Troy Percival | 190 | 170 | 20 |
| 2003-05-15 | @ NYA | 39 | L 4-10 | 19-20 | 3 | 29,670 | Aaron Sele | Jeff Weaver | Jeff Weaver | Aaron Sele | | 194 | 180 | 14 |
| 2003-05-16 | @ BOS | 40 | W 6-5 | 20-20 | 3 | 33,170 | Ramon Ortiz | Tim Wakefield | Francisco Rodriguez | Alan Embree | Troy Percival | 200 | 185 | 15 |
| 2003-05-17 | @ BOS | 41 | W 6-2 | 21-20 | 3 | 33,327 | Jarrod Washburn | Derek Lowe | Jarrod Washburn | Mike Timlin | Troy Percival | 206 | 187 | 19 |
| 2003-05-18 | @ BOS | 42 | L 3-5 | 21-21 | 3 | 33,347 | John Lackey | John Burkett | John Burkett | John Lackey | Robert Person | 209 | 192 | 17 |
| 2003-05-20 | vs BAL | 43 | W 7-6 | 22-21 | 3 | 24,657 | Kevin Appier | Rick Helling | Scott Schoeneweis | Jorge Julio | | 216 | 198 | 18 |
| 2003-05-21 | vs BAL | 44 | L 6-7 | 22-22 | 3 | 24,000 | Aaron Sele | Sidney Ponson | Sidney Ponson | Aaron Sele | Jorge Julio | 222 | 205 | 17 |
| 2003-05-22 | vs BAL | 45 | L 4-7 | 22-23 | 3 | 28,958 | Ramon Ortiz | Jason Johnson | Willis Roberts | Troy Percival | Jorge Julio | 226 | 212 | 14 |
| 2003-05-23 | vs TBA | 46 | L 1-3 | 22-24 | 4 | 37,902 | Jarrod Washburn | Geremi Gonzalez | Geremi Gonzalez | Jarrod Washburn | Lance Carter | 227 | 215 | 12 |
| 2003-05-24 | vs TBA | 47 | W 7-2 | 23-24 | 3 | 41,414 | John Lackey | Joe Kennedy | John Lackey | Joe Kennedy | | 234 | 217 | 17 |
| 2003-05-25 | vs TBA | 48 | W 6-1 | 24-24 | 3 | 34,777 | Kevin Appier | Dewon Brazelton | Kevin Appier | Dewon Brazelton | | 240 | 218 | 22 |
| 2003-05-27 | @ BAL | 49 | L 4-12 | 24-25 | 3 | 20,100 | Aaron Sele | Sidney Ponson | Sidney Ponson | Aaron Sele | | 244 | 230 | 14 |
| 2003-05-28 | @ BAL | 50 | L 2-6 | 24-26 | 3 | 20,366 | Ramon Ortiz | Jason Johnson | Jason Johnson | Ramon Ortiz | | 246 | 236 | 10 |
| 2003-05-29 | @ TBA | 51 | W 2-1 | 25-26 | 3 | 8,876 | Jarrod Washburn | Victor Zambrano | Jarrod Washburn | Victor Zambrano | Brendan Donnelly | 248 | 237 | 11 |
| 2003-05-30 | @ TBA | 52 | L 6-8 | 25-27 | 3 | 9,574 | John Lackey | Dewon Brazelton | Dewon Brazelton | John Lackey | Lance Carter | 254 | 245 | 9 |
| 2003-05-31 | @ TBA | 53 | W 6-1 | 26-27 | 3 | 14,546 | Kevin Appier | Joe Kennedy | Kevin Appier | Joe Kennedy | | 260 | 246 | 14 |
| 2003-06-01 | @ TBA | 54 | W 9-4 | 27-27 | 3 | 15,313 | Aaron Sele | Carlos Reyes | Aaron Sele | Carlos Reyes | | 269 | 250 | 19 |
| 2003-06-03 | @ MON | 55 | W 15-4 | 28-27 | 3 | 10,034 | Ramon Ortiz | Tomo Ohka | Ramon Ortiz | Tomo Ohka | | 284 | 254 | 30 |
| 2003-06-04 | @ MON | 56 | W 11-2 | 29-27 | 3 | 10,501 | Jarrod Washburn | Sun-Woo Kim | Jarrod Washburn | Sun-Woo Kim | | 295 | 256 | 39 |
| 2003-06-05 | @ MON | 57 | L 7-8 | 29-28 | 3 | 10,598 | John Lackey | Javier Vazquez | Joey Eischen | Mickey Callaway | | 302 | 264 | 38 |
| 2003-06-06 | @ FLO | 58 | L 1-4 | 29-29 | 3 | 13,188 | Kevin Appier | Carl Pavano | Carl Pavano | Kevin Appier | Braden Looper | 303 | 268 | 35 |
| 2003-06-07 | @ FLO | 59 | W 9-2 | 30-29 | 3 | 23,483 | Aaron Sele | Tommy Phelps | Aaron Sele | Tommy Phelps | | 312 | 270 | 42 |
| 2003-06-08 | @ FLO | 60 | W 8-5 | 31-29 | 3 | 12,620 | Ramon Ortiz | Brad Penny | Ramon Ortiz | Brad Penny | Troy Percival | 320 | 275 | 45 |
| 2003-06-09 | vs PHI | 61 | L 0-3 | 31-30 | 3 | 25,902 | Jarrod Washburn | Vicente Padilla | Vicente Padilla | Jarrod Washburn | Jose Mesa | 320 | 278 | 42 |
| 2003-06-10 | vs PHI | 62 | W 2-1 | 32-30 | 3 | 34,037 | John Lackey | Brandon Duckworth | John Lackey | Brandon Duckworth | Troy Percival | 322 | 279 | 43 |
| 2003-06-11 | vs PHI | 63 | W 5-3 | 33-30 | 3 | 31,130 | Kevin Appier | Brett Myers | Ben Weber | Brett Myers | Troy Percival | 327 | 282 | 45 |
| 2003-06-13 | vs NYN | 64 | L 3-7 | 33-31 | 3 | 38,294 | Aaron Sele | Michael Bacsik | Michael Bacsik | Aaron Sele | | 330 | 289 | 41 |
| 2003-06-14 | vs NYN | 65 | W 13-3 | 34-31 | 3 | 43,449 | Ramon Ortiz | Jason Roach | Ramon Ortiz | Jason Roach | | 343 | 292 | 51 |
| 2003-06-15 | vs NYN | 66 | L 0-8 | 34-32 | 3 | 43,721 | Jarrod Washburn | Steve Trachsel | Steve Trachsel | Jarrod Washburn | | 343 | 300 | 43 |
| 2003-06-16 | @ SEA | 67 | L 3-6 | 34-33 | 3 | 41,599 | John Lackey | Joel Pineiro | Joel Pineiro | John Lackey | Arthur Rhodes | 346 | 306 | 40 |
| 2003-06-17 | @ SEA | 68 | L 4-8 | 34-34 | 3 | 39,054 | Kevin Appier | Ryan Franklin | Ryan Franklin | Kevin Appier | | 350 | 314 | 36 |
| 2003-06-18 | @ SEA | 69 | L 0-2 | 34-35 | 3 | 43,473 | Aaron Sele | Freddy Garcia | Freddy Garcia | Aaron Sele | Arthur Rhodes | 350 | 316 | 34 |
| 2003-06-19 | @ SEA | 70 | W 2-0 | 35-35 | 3 | 45,758 | Ramon Ortiz | Jamie Moyer | Ramon Ortiz | Jamie Moyer | Troy Percival | 352 | 316 | 36 |
| 2003-06-20 | @ LAN | 71 | L 2-5 | 35-36 | 3 | 54,573 | Jarrod Washburn | Hideo Nomo | Hideo Nomo | Jarrod Washburn | Eric Gagne | 354 | 321 | 33 |
| 2003-06-21 | @ LAN | 72 | L 2-4 | 35-37 | 3 | 51,874 | John Lackey | Andy Ashby | Andy Ashby | John Lackey | Eric Gagne | 356 | 325 | 31 |
| 2003-06-22 | @ LAN | 73 | W 6-3 | 36-37 | 3 | 54,631 | Kevin Appier | Kevin Brown | Kevin Appier | Kevin Brown | Troy Percival | 362 | 328 | 34 |
| 2003-06-24 | vs SEA | 74 | L 4-6 | 36-38 | 3 | 39,121 | Aaron Sele | Freddy Garcia | Freddy Garcia | Aaron Sele | Jeff Nelson | 366 | 334 | 32 |
| 2003-06-25 | vs SEA | 75 | W 6-3 | 37-38 | 3 | 40,651 | Ramon Ortiz | Jamie Moyer | Ramon Ortiz | Jamie Moyer | Troy Percival | 372 | 337 | 35 |
| 2003-06-26 | vs SEA | 76 | L 6-10 | 37-39 | 3 | 32,889 | Jarrod Washburn | Gil Meche | Gil Meche | Jarrod Washburn | Shigetoshi Hasegawa | 378 | 347 | 31 |
| 2003-06-27 | vs LAN | 77 | W 3-0 | 38-39 | 3 | 43,700 | John Lackey | Kevin Brown | John Lackey | Kevin Brown | Troy Percival | 381 | 347 | 34 |
| 2003-06-28 | vs LAN | 78 | W 3-1 | 39-39 | 3 | 43,726 | Kevin Appier | Kazuhisa Ishii | Kevin Appier | Kazuhisa Ishii | Troy Percival | 384 | 348 | 36 |
| 2003-06-29 | vs LAN | 79 | W 3-1 | 40-39 | 3 | 43,766 | Aaron Sele | Odalis Perez | Aaron Sele | Odalis Perez | Troy Percival | 387 | 349 | 38 |
| 2003-06-30 | vs TEX | 80 | L 3-6 | 40-40 | 3 | 28,328 | Ramon Ortiz | John Thomson | John Thomson | Ramon Ortiz | Ugueth Urbina | 390 | 355 | 35 |
| 2003-07-01 | vs TEX | 81 | W 7-5 | 41-40 | 3 | 26,715 | Jarrod Washburn | Ismael Valdez | Jarrod Washburn | Ismael Valdez | Troy Percival | 397 | 360 | 37 |
| 2003-07-02 | vs TEX | 82 | W 5-0 | 42-40 | 3 | 33,114 | John Lackey | Joaquin Benoit | John Lackey | Joaquin Benoit | | 402 | 360 | 42 |
| 2003-07-03 | vs TEX | 83 | L 5-6 | 42-41 | 3 | 42,579 | Kevin Appier | Tony Mounce | Tony Mounce | Kevin Appier | Ugueth Urbina | 407 | 366 | 41 |
| 2003-07-04 | @ OAK | 84 | W 1-0 | 43-41 | 3 | 33,134 | Aaron Sele | Mark Mulder | Aaron Sele | Mark Mulder | Troy Percival | 408 | 366 | 42 |
| 2003-07-05 | @ OAK | 85 | W 6-3 | 44-41 | 3 | 55,601 | Ramon Ortiz | Aaron Harang | Ramon Ortiz | Aaron Harang | Troy Percival | 414 | 369 | 45 |
| 2003-07-06 | @ OAK | 86 | L 5-6 | 44-42 | 3 | 25,084 | Jarrod Washburn | Tim Hudson | Keith Foulke | Scott Schoeneweis | | 419 | 375 | 44 |
| 2003-07-08 | vs KCA | 87 | L 0-4 | 44-43 | 3 | 34,283 | John Lackey | Darrell May | Darrell May | John Lackey | | 419 | 379 | 40 |
| 2003-07-09 | vs KCA | 88 | W 5-3 | 45-43 | 3 | 34,196 | Kevin Appier | Jeremy Affeldt | Francisco Rodriguez | Jeremy Affeldt | Troy Percival | 424 | 382 | 42 |
| 2003-07-10 | vs KCA | 89 | W 7-1 | 46-43 | 3 | 38,836 | Aaron Sele | Chris George | Aaron Sele | Chris George | | 431 | 383 | 48 |
| 2003-07-11 | vs MIN | 90 | W 5-0 | 47-43 | 3 | 43,442 | Ramon Ortiz | Johan Santana | Ramon Ortiz | Johan Santana | Brendan Donnelly | 436 | 383 | 53 |
| 2003-07-12 | vs MIN | 91 | W 6-1 | 48-43 | 3 | 43,174 | Jarrod Washburn | Brad Radke | Jarrod Washburn | Brad Radke | | 442 | 384 | 58 |
| 2003-07-13 | vs MIN | 92 | W 8-3 | 49-43 | 3 | 38,835 | John Lackey | Kyle Lohse | John Lackey | Kyle Lohse | | 450 | 387 | 63 |
| 2003-07-17 | @ BAL | 93 | L 1-2 | 49-44 | 3 | 32,554 | Ramon Ortiz | Rodrigo Lopez | Rodrigo Lopez | Ramon Ortiz | Jorge Julio | 451 | 389 | 62 |
| 2003-07-18 | @ BAL | 94 | L 5-6 | 49-45 | 3 | 33,612 | Jarrod Washburn | Rick Helling | Kerry Ligtenberg | Francisco Rodriguez | Jorge Julio | 456 | 395 | 61 |
| 2003-07-19 | @ BAL | 95 | L 4-8 | 49-46 | 3 | 37,507 | Kevin Appier | Sidney Ponson | Sidney Ponson | Kevin Appier | Hector Carrasco | 460 | 403 | 57 |
| 2003-07-20 | @ BAL | 96 | L 6-7 | 49-47 | 3 | 40,046 | John Lackey | Jason Johnson | Jason Johnson | John Lackey | Jorge Julio | 466 | 410 | 56 |
| 2003-07-21 | @ TBA | 97 | L 2-3 | 49-48 | 3 | 9,673 | Aaron Sele | Rob Bell | Rob Bell | Aaron Sele | Travis Harper | 468 | 413 | 55 |
| 2003-07-22 | @ TBA | 98 | W 3-1 | 50-48 | 3 | 21,241 | Ramon Ortiz | Joe Kennedy | Ramon Ortiz | Joe Kennedy | Troy Percival | 471 | 414 | 57 |
| 2003-07-23 | @ TEX | 99 | L 9-12 | 50-49 | 3 | 24,093 | Jarrod Washburn | Ismael Valdez | Erasmo Ramirez | Jarrod Washburn | Francisco Cordero | 480 | 426 | 54 |
| 2003-07-24 | @ TEX | 100 | W 10-6 | 51-49 | 3 | 28,478 | Kevin Appier | Joaquin Benoit | Kevin Appier | Joaquin Benoit | Troy Percival | 490 | 432 | 58 |
| 2003-07-25 | vs OAK | 101 | L 2-3 | 51-50 | 3 | 43,797 | John Lackey | Ted Lilly | Ted Lilly | Brendan Donnelly | Keith Foulke | 492 | 435 | 57 |
| 2003-07-26 | vs OAK | 102 | L 1-8 | 51-51 | 3 | 43,279 | Aaron Sele | Rich Harden | Rich Harden | Aaron Sele | | 493 | 443 | 50 |
| 2003-07-27 | vs OAK | 103 | L 1-10 | 51-52 | 3 | 40,342 | Ramon Ortiz | Tim Hudson | Tim Hudson | Ramon Ortiz | | 494 | 453 | 41 |
| 2003-07-28 | vs OAK | 104 | W 2-1 | 52-52 | 3 | 38,402 | Jarrod Washburn | Barry Zito | Brendan Donnelly | Ricardo Rincon | Troy Percival | 496 | 454 | 42 |
| 2003-07-29 | vs NYA | 105 | L 2-6 | 52-53 | 3 | 43,817 | Kevin Appier | Andy Pettitte | Andy Pettitte | Kevin Appier | | 498 | 460 | 38 |
| 2003-07-30 | vs NYA | 106 | L 0-8 | 52-54 | 3 | 43,856 | John Lackey | Roger Clemens | Roger Clemens | John Lackey | | 498 | 468 | 30 |
| 2003-07-31 | vs NYA | 107 | L 1-2 | 52-55 | 3 | 43,871 | Aaron Sele | David Wells | Armando Benitez | Troy Percival | Mariano Rivera | 499 | 470 | 29 |
| 2003-08-01 | vs TOR | 108 | W 5-0 | 53-55 | 3 | 42,635 | Ramon Ortiz | Roy Halladay | Ramon Ortiz | Roy Halladay | | 504 | 470 | 34 |
| 2003-08-02 | vs TOR | 109 | L 1-6 | 53-56 | 3 | 43,087 | Jarrod Washburn | Corey Thurman | Corey Thurman | Jarrod Washburn | | 505 | 476 | 29 |
| 2003-08-03 | vs TOR | 110 | L 0-4 | 53-57 | 3 | 42,198 | Scot Shields | Kelvim Escobar | Kelvim Escobar | Scot Shields | Cliff Politte | 505 | 480 | 25 |
| 2003-08-05 | @ BOS | 111 | L 9-10 | 53-58 | 3 | 34,678 | John Lackey | Jeff Suppan | Mike Timlin | Brendan Donnelly | Byung-Hyun Kim | 514 | 490 | 24 |
| 2003-08-06 | @ BOS | 112 | L 2-4 | 53-59 | 3 | 35,040 | Aaron Sele | Pedro Martinez | Pedro Martinez | Aaron Sele | | 516 | 494 | 22 |
| 2003-08-07 | @ BOS | 113 | L 3-9 | 53-60 | 3 | 34,570 | Ramon Ortiz | John Burkett | John Burkett | Ramon Ortiz | | 519 | 503 | 16 |
| 2003-08-08 | @ CLE | 114 | W 5-2 | 54-60 | 3 | 26,175 | Jarrod Washburn | Jason Davis | Jarrod Washburn | Jason Davis | | 524 | 505 | 19 |
| 2003-08-09 | @ CLE | 115 | L 2-3 | 54-62 | 3 | 26,391 | Kevin Gregg | Brian Anderson | Jack Cressend | Ben Weber | | 526 | 508 | 18 |
| 2003-08-09 | @ CLE | 116 | L 2-3 | 54-62 | 3 | 20,116 | Scot Shields | Jason Stanford | Jason Boyd | Scot Shields | Danys Baez | 528 | 511 | 17 |
| 2003-08-10 | @ CLE | 117 | L 1-3 | 54-63 | 3 | 23,576 | John Lackey | CC Sabathia | CC Sabathia | John Lackey | Rafael Betancourt | 529 | 514 | 15 |
| 2003-08-11 | vs CHA | 118 | W 10-8 | 55-63 | 3 | 35,889 | Aaron Sele | Bartolo Colon | Ben Weber | Bartolo Colon | | 539 | 522 | 17 |
| 2003-08-12 | vs CHA | 119 | L 4-10 | 55-64 | 3 | 36,458 | Ramon Ortiz | Neal Cotts | Dan Wright | Ramon Ortiz | | 543 | 532 | 11 |
| 2003-08-13 | vs CHA | 120 | W 2-1 | 56-64 | 3 | 37,563 | Jarrod Washburn | Mark Buehrle | Francisco Rodriguez | Mark Buehrle | Troy Percival | 545 | 533 | 12 |
| 2003-08-14 | vs CHA | 121 | W 5-1 | 57-64 | 3 | 35,056 | Scot Shields | Jon Garland | Scot Shields | Jon Garland | Troy Percival | 550 | 534 | 16 |
| 2003-08-15 | vs DET | 122 | W 3-1 | 58-64 | 3 | 43,174 | John Lackey | Nate Cornejo | John Lackey | Nate Cornejo | Troy Percival | 553 | 535 | 18 |
| 2003-08-16 | vs DET | 123 | W 11-7 | 59-64 | 3 | 42,337 | Aaron Sele | Wil Ledezma | Gary Glover | Wil Ledezma | | 564 | 542 | 22 |
| 2003-08-17 | vs DET | 124 | W 11-6 | 60-64 | 3 | 40,745 | Ramon Ortiz | Jeremy Bonderman | Ramon Ortiz | Jeremy Bonderman | | 575 | 548 | 27 |
| 2003-08-18 | @ CHA | 125 | L 2-4 | 60-65 | 3 | 32,381 | Jarrod Washburn | Mark Buehrle | Tom Gordon | Jarrod Washburn | | 577 | 552 | 25 |
| 2003-08-19 | @ CHA | 126 | L 2-5 | 60-66 | 3 | 22,396 | Scot Shields | Jon Garland | Jon Garland | Scot Shields | Tom Gordon | 579 | 557 | 22 |
| 2003-08-20 | @ CHA | 127 | L 3-5 | 60-67 | 3 | 17,879 | John Lackey | Esteban Loaiza | Esteban Loaiza | John Lackey | Damaso Marte | 582 | 562 | 20 |
| 2003-08-21 | @ DET | 128 | W 10-7 | 61-67 | 3 | 12,236 | Aaron Sele | Shane Loux | Aaron Sele | Matt Roney | | 592 | 569 | 23 |
| 2003-08-22 | @ DET | 129 | W 6-5 | 62-67 | 3 | 21,955 | Ramon Ortiz | Jeremy Bonderman | Ramon Ortiz | Jeremy Bonderman | Troy Percival | 598 | 574 | 24 |
| 2003-08-23 | @ DET | 130 | W 14-8 | 63-67 | 3 | 26,463 | Jarrod Washburn | Nate Robertson | Brendan Donnelly | Chris Spurling | | 612 | 582 | 30 |
| 2003-08-24 | @ DET | 131 | L 9-10 | 63-68 | 3 | 17,382 | Scot Shields | Mike Maroth | Jamie Walker | Troy Percival | | 621 | 592 | 29 |
| 2003-08-26 | vs MIN | 132 | L 0-3 | 63-69 | 3 | 35,415 | John Lackey | Brad Radke | Brad Radke | John Lackey | | 621 | 595 | 26 |
| 2003-08-27 | vs MIN | 133 | W 5-4 | 64-69 | 3 | 36,323 | Aaron Sele | Kenny Rogers | Ben Weber | Juan Rincon | Troy Percival | 626 | 599 | 27 |
| 2003-08-28 | vs MIN | 134 | L 1-6 | 64-70 | 3 | 33,760 | Ramon Ortiz | Kyle Lohse | Kyle Lohse | Ramon Ortiz | | 627 | 605 | 22 |
| 2003-08-29 | @ KCA | 135 | W 10-3 | 65-70 | 3 | 23,836 | Jarrod Washburn | Jimmy Gobble | Jarrod Washburn | Jimmy Gobble | | 637 | 608 | 29 |
| 2003-08-31 | @ KCA | 136 | W 7-4 | 66-70 | 3 | 21,324 | Scot Shields | Brian Anderson | Scot Shields | Brian Anderson | Troy Percival | 644 | 612 | 32 |
| 2003-09-01 | @ MIN | 137 | W 10-2 | 67-70 | 3 | 22,208 | John Lackey | Kenny Rogers | John Lackey | Kenny Rogers | | 654 | 614 | 40 |
| 2003-09-02 | @ MIN | 138 | L 6-12 | 67-71 | 3 | 13,307 | Aaron Sele | Kyle Lohse | Kyle Lohse | Aaron Sele | | 660 | 626 | 34 |
| 2003-09-03 | @ MIN | 139 | L 5-6 | 67-72 | 3 | 11,434 | Ramon Ortiz | Grant Balfour | Eddie Guardado | Troy Percival | | 665 | 632 | 33 |
| 2003-09-05 | vs KCA | 140 | L 0-5 | 67-73 | 3 | 43,111 | Jarrod Washburn | Brian Anderson | Brian Anderson | Jarrod Washburn | | 665 | 637 | 28 |
| 2003-09-06 | vs KCA | 141 | W 6-5 | 69-73 | 3 | 0 | Scot Shields | Darrell May | Ben Weber | Jason Grimsley | Troy Percival | 671 | 642 | 29 |
| 2003-09-06 | vs KCA | 142 | W 3-1 | 69-73 | 3 | 43,044 | Kevin Gregg | Jamey Wright | Kevin Gregg | Jamey Wright | Troy Percival | 674 | 643 | 31 |
| 2003-09-07 | vs KCA | 143 | L 0-3 | 69-74 | 3 | 38,943 | John Lackey | Paul Abbott | Paul Abbott | John Lackey | Jeremy Affeldt | 674 | 646 | 28 |
| 2003-09-08 | @ OAK | 144 | W 3-1 | 70-74 | 3 | 20,760 | Aaron Sele | Tim Hudson | Francisco Rodriguez | Tim Hudson | Troy Percival | 677 | 647 | 30 |
| 2003-09-09 | @ OAK | 145 | L 1-8 | 70-75 | 3 | 17,253 | Chris Bootcheck | Justin Duchscherer | Justin Duchscherer | Chris Bootcheck | | 678 | 655 | 23 |
| 2003-09-10 | @ OAK | 146 | L 0-3 | 70-76 | 3 | 31,359 | Jarrod Washburn | Ted Lilly | Ted Lilly | Jarrod Washburn | Keith Foulke | 678 | 658 | 20 |
| 2003-09-11 | @ OAK | 147 | L 4-14 | 70-77 | 3 | 26,755 | Scot Shields | Rich Harden | Rich Harden | Scot Shields | | 682 | 672 | 10 |
| 2003-09-12 | @ SEA | 148 | L 4-7 | 70-78 | 3 | 41,601 | John Lackey | Jamie Moyer | Jamie Moyer | John Lackey | Shigetoshi Hasegawa | 686 | 679 | 7 |
| 2003-09-13 | @ SEA | 149 | L 1-5 | 70-79 | 3 | 45,552 | Aaron Sele | Freddy Garcia | Freddy Garcia | Francisco Rodriguez | | 687 | 684 | 3 |
| 2003-09-14 | @ SEA | 150 | W 2-1 | 71-79 | 3 | 45,861 | Kevin Gregg | Ryan Franklin | Kevin Gregg | Ryan Franklin | Troy Percival | 689 | 685 | 4 |
| 2003-09-15 | vs OAK | 151 | L 4-7 | 71-80 | 3 | 34,861 | Ramon Ortiz | Ted Lilly | Ted Lilly | Ramon Ortiz | Keith Foulke | 693 | 692 | 1 |
| 2003-09-16 | vs OAK | 152 | W 6-5 | 72-80 | 3 | 36,446 | Jarrod Washburn | Rich Harden | Derrick Turnbow | Jim Mecir | | 699 | 697 | 2 |
| 2003-09-17 | vs OAK | 153 | L 1-2 | 72-81 | 3 | 32,503 | Scot Shields | Barry Zito | Barry Zito | Scot Shields | Jim Mecir | 700 | 699 | 1 |
| 2003-09-19 | @ TEX | 154 | L 2-3 | 72-82 | 3 | 23,725 | John Lackey | R.A. Dickey | R.A. Dickey | John Lackey | Francisco Cordero | 702 | 702 | 0 |
| 2003-09-20 | @ TEX | 155 | L 4-13 | 72-83 | 3 | 47,506 | Aaron Sele | Colby Lewis | Colby Lewis | Aaron Sele | | 706 | 715 | -9 |
| 2003-09-21 | @ TEX | 156 | W 11-6 | 73-83 | 3 | 32,689 | Ramon Ortiz | John Thomson | Ramon Ortiz | Ron Mahay | | 717 | 721 | -4 |
| 2003-09-22 | vs SEA | 157 | L 1-5 | 73-84 | 3 | 35,537 | Jarrod Washburn | Jamie Moyer | Jamie Moyer | Jarrod Washburn | | 718 | 726 | -8 |
| 2003-09-23 | vs SEA | 158 | W 2-1 | 74-84 | 3 | 37,645 | Scot Shields | Freddy Garcia | Francisco Rodriguez | Shigetoshi Hasegawa | | 720 | 727 | -7 |
| 2003-09-24 | vs SEA | 159 | W 4-0 | 75-84 | 3 | 30,917 | John Lackey | Gil Meche | John Lackey | Gil Meche | | 724 | 727 | -3 |
| 2003-09-26 | vs TEX | 160 | W 5-3 | 76-84 | 3 | 43,485 | Aaron Sele | R.A. Dickey | Derrick Turnbow | Ron Mahay | Francisco Rodriguez | 729 | 730 | -1 |
| 2003-09-27 | vs TEX | 161 | L 3-12 | 76-85 | 3 | 43,218 | Ramon Ortiz | Colby Lewis | Colby Lewis | Ramon Ortiz | | 732 | 742 | -10 |
| 2003-09-28 | vs TEX | 162 | W 4-1 | 77-85 | 3 | 42,798 | Scot Shields | John Thomson | Scot Shields | John Thomson | Brendan Donnelly | 736 | 743 | -7 |