| 1998-03-31 | @ BAL | 1 | W 4-1 | 1-0 | 4 | 46,820 | Tim Belcher | Mike Mussina | Tim Belcher | Mike Mussina | Jeff Montgomery | 4 | 1 | 3 |
| 1998-04-01 | @ BAL | 2 | L 1-10 | 1-1 | 4 | 38,623 | Glendon Rusch | Scott Erickson | Scott Erickson | Glendon Rusch | | 5 | 11 | -6 |
| 1998-04-02 | @ BAL | 3 | L 3-4 | 1-2 | 5 | 39,435 | Pat Rapp | Jimmy Key | Armando Benitez | Jeff Montgomery | | 8 | 15 | -7 |
| 1998-04-03 | @ MIN | 4 | W 9-5 | 2-2 | 3 | 43,848 | Chris Haney | Brad Radke | Chris Haney | Brad Radke | | 17 | 20 | -3 |
| 1998-04-04 | @ MIN | 5 | W 3-2 | 3-2 | 2 | 18,589 | Hipolito Pichardo | Mike Morgan | Brian Bevil | Eddie Guardado | Jeff Montgomery | 20 | 22 | -2 |
| 1998-04-05 | @ MIN | 6 | L 1-10 | 3-3 | 2 | 10,851 | Tim Belcher | Eric Milton | Eric Milton | Tim Belcher | | 21 | 32 | -11 |
| 1998-04-07 | vs BAL | 7 | L 7-11 | 3-4 | 4 | 40,419 | Glendon Rusch | Scott Erickson | Scott Erickson | Glendon Rusch | | 28 | 43 | -15 |
| 1998-04-09 | vs BAL | 8 | L 1-2 | 3-5 | 4 | 13,790 | Pat Rapp | Jimmy Key | Jimmy Key | Jose Rosado | Armando Benitez | 29 | 45 | -16 |
| 1998-04-10 | vs MIN | 9 | W 5-4 | 4-5 | 3 | 14,341 | Chris Haney | Mike Morgan | Brian Bevil | Rick Aguilera | | 34 | 49 | -15 |
| 1998-04-11 | vs MIN | 10 | L 3-8 | 4-6 | 4 | 18,087 | Tim Belcher | Eric Milton | Eric Milton | Tim Belcher | | 37 | 57 | -20 |
| 1998-04-12 | vs MIN | 11 | L 2-7 | 4-7 | 4 | 11,875 | Hipolito Pichardo | Bob Tewksbury | Bob Tewksbury | Hipolito Pichardo | Rick Aguilera | 39 | 64 | -25 |
| 1998-04-13 | vs TOR | 12 | W 11-1 | 5-7 | 3 | 11,749 | Glendon Rusch | Pat Hentgen | Glendon Rusch | Pat Hentgen | | 50 | 65 | -15 |
| 1998-04-14 | vs TOR | 13 | L 1-5 | 5-8 | 3 | 11,194 | Pat Rapp | Juan Guzman | Juan Guzman | Pat Rapp | Paul Quantrill | 51 | 70 | -19 |
| 1998-04-15 | vs TOR | 14 | W 7-3 | 6-8 | 3 | 11,316 | Chris Haney | Woody Williams | Chris Haney | Woody Williams | | 58 | 73 | -15 |
| 1998-04-16 | @ OAK | 15 | L 7-12 | 6-9 | 4 | 6,456 | Tim Belcher | Tom Candiotti | Tom Candiotti | Tim Belcher | | 65 | 85 | -20 |
| 1998-04-17 | @ OAK | 16 | W 4-1 | 7-9 | 3 | 7,402 | Hipolito Pichardo | Mike Oquist | Scott Service | Jim Dougherty | Jeff Montgomery | 69 | 86 | -17 |
| 1998-04-18 | @ OAK | 17 | L 2-3 | 7-10 | 3 | 10,274 | Glendon Rusch | Kenny Rogers | Kenny Rogers | Glendon Rusch | Billy Taylor | 71 | 89 | -18 |
| 1998-04-19 | @ OAK | 18 | W 7-3 | 8-10 | 2 | 14,127 | Pat Rapp | Ariel Prieto | Pat Rapp | Ariel Prieto | Jose Rosado | 78 | 92 | -14 |
| 1998-04-20 | @ SEA | 19 | L 7-8 | 8-11 | 2 | 38,345 | Chris Haney | Randy Johnson | Felipe Lira | Danny Rios | Bobby Ayala | 85 | 100 | -15 |
| 1998-04-21 | @ SEA | 20 | W 5-3 | 9-11 | 2 | 21,547 | Tim Belcher | Jamie Moyer | Brian Bevil | Tony Fossas | Jeff Montgomery | 90 | 103 | -13 |
| 1998-04-22 | @ SEA | 21 | L 5-11 | 9-12 | 2 | 22,698 | Hipolito Pichardo | Jeff Fassero | Jeff Fassero | Hipolito Pichardo | | 95 | 114 | -19 |
| 1998-04-24 | vs TEX | 22 | W 11-4 | 10-12 | 2 | 17,718 | Glendon Rusch | John Burkett | Glendon Rusch | John Burkett | | 106 | 118 | -12 |
| 1998-04-25 | vs TEX | 23 | L 8-11 | 10-13 | 2 | 24,453 | Pat Rapp | Bobby Witt | Bobby Witt | Pat Rapp | John Wetteland | 114 | 129 | -15 |
| 1998-04-26 | vs TEX | 24 | L 4-11 | 10-14 | 3 | 15,768 | Chris Haney | Aaron Sele | Aaron Sele | Chris Haney | | 118 | 140 | -22 |
| 1998-04-28 | vs SEA | 25 | L 1-5 | 10-15 | 3 | 11,630 | Tim Belcher | Randy Johnson | Randy Johnson | Scott Service | | 119 | 145 | -26 |
| 1998-04-29 | @ TOR | 26 | W 7-2 | 11-15 | 3 | 25,644 | Hipolito Pichardo | Pat Hentgen | Hipolito Pichardo | Pat Hentgen | | 126 | 147 | -21 |
| 1998-04-30 | @ TOR | 27 | W 7-4 | 12-15 | 2 | 26,690 | Glendon Rusch | Juan Guzman | Glendon Rusch | Juan Guzman | Jeff Montgomery | 133 | 151 | -18 |
| 1998-05-01 | vs NYA | 28 | L 1-2 | 12-16 | 2 | 19,002 | Pat Rapp | Hideki Irabu | Hideki Irabu | Pat Rapp | Mariano Rivera | 134 | 153 | -19 |
| 1998-05-02 | vs NYA | 29 | L 6-12 | 12-17 | 2 | 22,743 | Chris Haney | Andy Pettitte | Andy Pettitte | Chris Haney | | 140 | 165 | -25 |
| 1998-05-03 | vs NYA | 30 | L 1-10 | 12-18 | 3 | 22,609 | Tim Belcher | Ramiro Mendoza | Ramiro Mendoza | Tim Belcher | | 141 | 175 | -34 |
| 1998-05-05 | vs TBA | 31 | W 4-2 | 13-18 | 3 | 12,096 | Hipolito Pichardo | Wilson Alvarez | Hipolito Pichardo | Wilson Alvarez | Jeff Montgomery | 145 | 177 | -32 |
| 1998-05-06 | vs TBA | 32 | L 0-5 | 13-19 | 3 | 11,401 | Glendon Rusch | Rolando Arrojo | Rolando Arrojo | Glendon Rusch | | 145 | 182 | -37 |
| 1998-05-07 | vs BOS | 33 | W 5-3 | 14-19 | 2 | 14,703 | Pat Rapp | Brian Rose | Pat Rapp | Brian Rose | Jeff Montgomery | 150 | 185 | -35 |
| 1998-05-08 | vs BOS | 34 | L 3-14 | 14-20 | 3 | 24,439 | Chris Haney | Bret Saberhagen | Bret Saberhagen | Chris Haney | Rich Garces | 153 | 199 | -46 |
| 1998-05-09 | vs BOS | 35 | L 1-3 | 14-21 | 4 | 18,035 | Tim Belcher | Pedro Martinez | Pedro Martinez | Tim Belcher | Tom Gordon | 154 | 202 | -48 |
| 1998-05-10 | vs BOS | 36 | L 1-3 | 14-22 | 4 | 14,793 | Jose Rosado | Tim Wakefield | Tim Wakefield | Jose Rosado | Tom Gordon | 155 | 205 | -50 |
| 1998-05-12 | @ NYA | 37 | L 2-3 | 14-23 | 4 | 16,606 | Glendon Rusch | David Wells | David Wells | Glendon Rusch | Mariano Rivera | 157 | 208 | -51 |
| 1998-05-13 | @ TBA | 38 | W 4-0 | 15-23 | 4 | 25,224 | Pat Rapp | Tony Saunders | Pat Rapp | Tony Saunders | | 161 | 208 | -47 |
| 1998-05-14 | @ TBA | 39 | W 10-2 | 16-23 | 4 | 24,296 | Tim Belcher | Dennis Springer | Tim Belcher | Dennis Springer | | 171 | 210 | -39 |
| 1998-05-15 | @ BOS | 40 | L 2-5 | 16-24 | 4 | 31,466 | Jose Rosado | Tim Wakefield | Tim Wakefield | Jose Rosado | Dennis Eckersley | 173 | 215 | -42 |
| 1998-05-16 | @ BOS | 41 | L 0-5 | 16-25 | 4 | 31,700 | Jamie Walker | Steve Avery | Steve Avery | Jamie Walker | Tom Gordon | 173 | 220 | -47 |
| 1998-05-17 | @ BOS | 42 | L 3-5 | 16-26 | 4 | 29,736 | Glendon Rusch | Derek Lowe | Ron Mahay | Glendon Rusch | Tom Gordon | 176 | 225 | -49 |
| 1998-05-19 | vs CLE | 43 | L 3-16 | 16-27 | 5 | 13,367 | Pat Rapp | Chad Ogea | Chad Ogea | Pat Rapp | | 179 | 241 | -62 |
| 1998-05-20 | vs CLE | 44 | L 5-14 | 16-28 | 5 | 13,575 | Tim Belcher | Charles Nagy | Charles Nagy | Tim Belcher | | 184 | 255 | -71 |
| 1998-05-21 | vs CLE | 45 | L 2-6 | 16-29 | 5 | 17,243 | Jose Rosado | Jaret Wright | Jaret Wright | Jose Rosado | | 186 | 261 | -75 |
| 1998-05-22 | @ TEX | 46 | L 10-13 | 16-30 | 5 | 38,411 | Jamie Walker | Bobby Witt | John Wetteland | Jeff Montgomery | | 196 | 274 | -78 |
| 1998-05-23 | @ TEX | 47 | L 3-7 | 16-31 | 5 | 46,372 | Glendon Rusch | Aaron Sele | Aaron Sele | Glendon Rusch | | 199 | 281 | -82 |
| 1998-05-24 | @ TEX | 48 | W 8-3 | 17-31 | 5 | 46,243 | Pat Rapp | Rick Helling | Pat Rapp | Rick Helling | Hipolito Pichardo | 207 | 284 | -77 |
| 1998-05-25 | @ ANA | 49 | W 6-4 | 18-31 | 5 | 21,065 | Tim Belcher | Ken Hill | Tim Belcher | Ken Hill | Jeff Montgomery | 213 | 288 | -75 |
| 1998-05-27 | @ ANA | 50 | W 4-0 | 19-31 | 5 | 17,810 | Jose Rosado | Omar Olivares | Jose Rosado | Omar Olivares | | 217 | 288 | -71 |
| 1998-05-29 | vs OAK | 51 | W 5-3 | 20-31 | 5 | 14,749 | Pat Rapp | Blake Stein | Chris Haney | Mike Mohler | Jeff Montgomery | 222 | 291 | -69 |
| 1998-05-30 | vs OAK | 52 | L 4-10 | 20-32 | 5 | 30,341 | Glendon Rusch | Jimmy Haynes | Billy Taylor | Hipolito Pichardo | | 226 | 301 | -75 |
| 1998-05-31 | vs OAK | 53 | W 10-4 | 21-32 | 5 | 27,126 | Tim Belcher | Kenny Rogers | Tim Belcher | T.J. Mathews | | 236 | 305 | -69 |
| 1998-06-01 | vs ANA | 54 | L 3-6 | 21-33 | 5 | 14,502 | Jose Rosado | Omar Olivares | Shigetoshi Hasegawa | Hipolito Pichardo | Troy Percival | 239 | 311 | -72 |
| 1998-06-02 | vs ANA | 55 | L 5-7 | 21-34 | 5 | 12,020 | Chris Haney | Jarrod Washburn | Jarrod Washburn | Chris Haney | Troy Percival | 244 | 318 | -74 |
| 1998-06-03 | vs CHA | 56 | L 5-10 | 21-35 | 5 | 13,280 | Pat Rapp | Jason Bere | Carlos Castillo | Pat Rapp | | 249 | 328 | -79 |
| 1998-06-04 | vs CHA | 57 | L 1-7 | 21-36 | 5 | 16,590 | Glendon Rusch | Jaime Navarro | Jaime Navarro | Glendon Rusch | | 250 | 335 | -85 |
| 1998-06-05 | @ HOU | 58 | W 3-0 | 22-36 | 4 | 27,895 | Tim Belcher | Pete Schourek | Tim Belcher | Pete Schourek | Jeff Montgomery | 253 | 335 | -82 |
| 1998-06-06 | @ HOU | 59 | L 0-6 | 22-37 | 5 | 25,516 | Jose Rosado | Jose Lima | Jose Lima | Jose Rosado | | 253 | 341 | -88 |
| 1998-06-07 | @ HOU | 60 | L 1-7 | 22-38 | 5 | 23,228 | Jim Pittsley | Shane Reynolds | Shane Reynolds | Jim Pittsley | | 254 | 348 | -94 |
| 1998-06-08 | vs MIL | 61 | W 8-7 | 23-38 | 5 | 13,565 | Pat Rapp | Jeff Juden | Pat Rapp | Jeff Juden | Jeff Montgomery | 262 | 355 | -93 |
| 1998-06-09 | vs MIL | 62 | L 3-6 | 23-39 | 5 | 12,775 | Glendon Rusch | Brad Woodall | Bob Wickman | Jeff Montgomery | Doug Jones | 265 | 361 | -96 |
| 1998-06-10 | vs MIL | 63 | L 6-9 | 23-40 | 5 | 12,477 | Tim Belcher | Cal Eldred | Bronswell Patrick | Hipolito Pichardo | | 271 | 370 | -99 |
| 1998-06-12 | vs DET | 64 | W 7-3 | 24-40 | 4 | 15,214 | Jose Rosado | Bryce Florie | Jose Rosado | Bryce Florie | | 278 | 373 | -95 |
| 1998-06-13 | vs DET | 65 | L 1-7 | 24-41 | 5 | 29,603 | Pat Rapp | Justin Thompson | Justin Thompson | Pat Rapp | | 279 | 380 | -101 |
| 1998-06-14 | vs DET | 66 | W 2-0 | 25-41 | 4 | 18,720 | Glendon Rusch | Seth Greisinger | Glendon Rusch | Seth Greisinger | | 281 | 380 | -99 |
| 1998-06-15 | @ CLE | 67 | W 7-6 | 26-41 | 4 | 43,246 | Tim Belcher | Dave Burba | Jeff Montgomery | Jose Mesa | Matt Whisenant | 288 | 386 | -98 |
| 1998-06-16 | @ CLE | 68 | L 1-9 | 26-42 | 4 | 43,184 | Hipolito Pichardo | Bartolo Colon | Bartolo Colon | Hipolito Pichardo | | 289 | 395 | -106 |
| 1998-06-17 | @ CLE | 69 | W 4-3 | 27-42 | 4 | 43,196 | Jose Rosado | Dwight Gooden | Jose Rosado | Dwight Gooden | Jeff Montgomery | 293 | 398 | -105 |
| 1998-06-18 | @ DET | 70 | W 5-3 | 28-42 | 4 | 11,057 | Pat Rapp | Justin Thompson | Pat Rapp | Justin Thompson | Jeff Montgomery | 298 | 401 | -103 |
| 1998-06-19 | @ DET | 71 | W 8-4 | 29-42 | 3 | 22,680 | Glendon Rusch | Seth Greisinger | Glendon Rusch | Seth Greisinger | Ricky Bones | 306 | 405 | -99 |
| 1998-06-20 | @ DET | 72 | L 3-4 | 29-43 | 4 | 19,629 | Tim Belcher | Brian Moehler | Brian Moehler | Tim Belcher | Todd Jones | 309 | 409 | -100 |
| 1998-06-21 | @ DET | 73 | W 6-5 | 30-43 | 3 | 18,105 | Hipolito Pichardo | Denny Harriger | Hipolito Pichardo | Denny Harriger | Jeff Montgomery | 315 | 414 | -99 |
| 1998-06-22 | @ CIN | 74 | W 3-0 | 31-43 | 3 | 18,687 | Jim Pittsley | Mike Remlinger | Jim Pittsley | Mike Remlinger | Jeff Montgomery | 318 | 414 | -96 |
| 1998-06-23 | @ CIN | 75 | W 6-4 | 32-43 | 3 | 18,063 | Pat Rapp | Scott Klingenbeck | Pat Rapp | Scott Klingenbeck | Scott Service | 324 | 418 | -94 |
| 1998-06-24 | vs PIT | 76 | L 3-10 | 32-44 | 4 | 18,007 | Glendon Rusch | Chris Peters | Chris Peters | Glendon Rusch | | 327 | 428 | -101 |
| 1998-06-25 | vs PIT | 77 | W 6-1 | 33-44 | 3 | 22,504 | Tim Belcher | Jon Lieber | Tim Belcher | Jon Lieber | | 333 | 429 | -96 |
| 1998-06-26 | vs CHN | 78 | W 6-3 | 34-44 | 3 | 39,008 | Hipolito Pichardo | Steve Trachsel | Hipolito Pichardo | Steve Trachsel | Jeff Montgomery | 339 | 432 | -93 |
| 1998-06-27 | vs CHN | 79 | W 4-3 | 35-44 | 3 | 39,295 | Jose Rosado | Kevin Tapani | Scott Service | Rod Beck | | 343 | 435 | -92 |
| 1998-06-28 | vs CHN | 80 | L 3-6 | 35-45 | 3 | 34,287 | Pat Rapp | Geremi Gonzalez | Geremi Gonzalez | Pat Rapp | Rod Beck | 346 | 441 | -95 |
| 1998-06-30 | @ SLN | 81 | W 6-1 | 36-45 | 3 | 41,801 | Glendon Rusch | Manny Aybar | Glendon Rusch | Manny Aybar | Scott Service | 352 | 442 | -90 |
| 1998-07-01 | @ SLN | 82 | W 6-4 | 37-45 | 3 | 36,144 | Tim Belcher | Kent Mercker | Tim Belcher | Kent Mercker | Jeff Montgomery | 358 | 446 | -88 |
| 1998-07-02 | @ SLN | 83 | L 0-3 | 37-46 | 3 | 42,803 | Hipolito Pichardo | Juan Acevedo | Juan Acevedo | Hipolito Pichardo | Jeff Brantley | 358 | 449 | -91 |
| 1998-07-03 | vs CLE | 84 | L 1-2 | 37-47 | 3 | 27,661 | Jose Rosado | Dwight Gooden | Paul Shuey | Jose Rosado | Michael Jackson | 359 | 451 | -92 |
| 1998-07-04 | vs CLE | 85 | W 5-3 | 38-47 | 3 | 34,270 | Pat Rapp | Charles Nagy | Pat Rapp | Charles Nagy | Jeff Montgomery | 364 | 454 | -90 |
| 1998-07-05 | vs CLE | 86 | L 3-12 | 38-48 | 3 | 15,507 | Glendon Rusch | Jaret Wright | Jaret Wright | Glendon Rusch | | 367 | 466 | -99 |
| 1998-07-09 | @ CHA | 87 | W 6-4 | 39-48 | 3 | 15,023 | Tim Belcher | Mike Sirotka | Tim Belcher | Mike Sirotka | Jeff Montgomery | 373 | 470 | -97 |
| 1998-07-10 | @ CHA | 88 | L 3-10 | 39-49 | 3 | 15,378 | Jose Rosado | Jaime Navarro | Jaime Navarro | Jose Rosado | | 376 | 480 | -104 |
| 1998-07-11 | @ CHA | 89 | L 3-4 | 39-50 | 3 | 21,814 | Pat Rapp | James Baldwin | James Baldwin | Pat Rapp | Matt Karchner | 379 | 484 | -105 |
| 1998-07-12 | @ CHA | 90 | W 4-3 | 40-50 | 3 | 32,929 | Glendon Rusch | Jim Parque | Scott Service | Matt Karchner | Jeff Montgomery | 383 | 487 | -104 |
| 1998-07-13 | @ DET | 91 | W 6-4 | 41-50 | 3 | 13,945 | Hipolito Pichardo | Frank Castillo | Matt Whisenant | Todd Jones | Jeff Montgomery | 389 | 491 | -102 |
| 1998-07-14 | @ DET | 92 | L 3-8 | 41-51 | 3 | 17,491 | Tim Belcher | Justin Thompson | Justin Thompson | Tim Belcher | | 392 | 499 | -107 |
| 1998-07-15 | @ OAK | 93 | W 5-1 | 42-51 | 2 | 9,619 | Jose Rosado | Tom Candiotti | Jose Rosado | Tom Candiotti | | 397 | 500 | -103 |
| 1998-07-16 | @ OAK | 94 | L 3-5 | 42-52 | 2 | 10,820 | Pat Rapp | Blake Stein | Blake Stein | Pat Rapp | Billy Taylor | 400 | 505 | -105 |
| 1998-07-17 | @ SEA | 95 | L 5-18 | 42-53 | 4 | 29,500 | Glendon Rusch | Bill Swift | Bill Swift | Glendon Rusch | | 405 | 523 | -118 |
| 1998-07-18 | @ SEA | 96 | L 5-8 | 42-54 | 4 | 42,633 | Hipolito Pichardo | Ken Cloude | Bobby Ayala | Scott Service | | 410 | 531 | -121 |
| 1998-07-19 | @ SEA | 97 | W 4-1 | 43-54 | 4 | 30,851 | Tim Belcher | Jeff Fassero | Tim Belcher | Jeff Fassero | Jeff Montgomery | 414 | 532 | -118 |
| 1998-07-21 | vs TEX | 98 | L 5-15 | 43-55 | 4 | 17,457 | Jose Rosado | Rick Helling | Rick Helling | Jose Rosado | | 419 | 547 | -128 |
| 1998-07-22 | vs TEX | 99 | W 7-4 | 44-55 | 3 | 14,660 | Pat Rapp | Aaron Sele | Pat Rapp | Aaron Sele | Jeff Montgomery | 426 | 551 | -125 |
| 1998-07-23 | vs TEX | 100 | L 4-8 | 44-56 | 4 | 21,656 | Glendon Rusch | Darren Oliver | Xavier Hernandez | Glendon Rusch | | 430 | 559 | -129 |
| 1998-07-24 | vs ANA | 101 | W 4-3 | 45-56 | 3 | 18,151 | Hipolito Pichardo | Chuck Finley | Hipolito Pichardo | Chuck Finley | Jeff Montgomery | 434 | 562 | -128 |
| 1998-07-25 | vs ANA | 102 | L 5-6 | 45-57 | 4 | 28,428 | Tim Belcher | Jarrod Washburn | Pep Harris | Tim Belcher | Mike Holtz | 439 | 568 | -129 |
| 1998-07-26 | vs ANA | 103 | W 9-4 | 46-57 | 3 | 20,702 | Jose Rosado | Omar Olivares | Jose Rosado | Omar Olivares | | 448 | 572 | -124 |
| 1998-07-27 | vs ANA | 104 | L 1-6 | 46-58 | 3 | 17,252 | Pat Rapp | Allen Watson | Allen Watson | Pat Rapp | Shigetoshi Hasegawa | 449 | 578 | -129 |
| 1998-07-28 | vs MIN | 105 | L 0-3 | 46-59 | 4 | 14,365 | Glendon Rusch | Brad Radke | Brad Radke | Glendon Rusch | Rick Aguilera | 449 | 581 | -132 |
| 1998-07-29 | vs MIN | 106 | L 3-5 | 46-60 | 4 | 14,362 | Hipolito Pichardo | Eric Milton | Eric Milton | Hipolito Pichardo | Rick Aguilera | 452 | 586 | -134 |
| 1998-07-30 | vs MIN | 107 | W 7-3 | 47-60 | 4 | 20,466 | Tim Belcher | Dan Serafini | Tim Belcher | Dan Serafini | | 459 | 589 | -130 |
| 1998-07-31 | vs BAL | 108 | W 9-6 | 48-60 | 4 | 25,007 | Jose Rosado | Scott Erickson | Jose Rosado | Scott Erickson | | 468 | 595 | -127 |
| 1998-08-01 | vs BAL | 109 | W 9-5 | 49-60 | 3 | 35,144 | Pat Rapp | Scott Kamieniecki | Chris Haney | Scott Kamieniecki | | 477 | 600 | -123 |
| 1998-08-02 | vs BAL | 110 | L 2-9 | 49-61 | 3 | 18,910 | Glendon Rusch | Sidney Ponson | Sidney Ponson | Glendon Rusch | | 479 | 609 | -130 |
| 1998-08-04 | @ MIN | 111 | W 12-4 | 50-61 | 3 | 11,014 | Hipolito Pichardo | Eric Milton | Hipolito Pichardo | Eric Milton | | 491 | 613 | -122 |
| 1998-08-05 | @ MIN | 112 | W 4-3 | 51-61 | 3 | 9,545 | Tim Belcher | Frankie Rodriguez | Tim Belcher | Frankie Rodriguez | Jeff Montgomery | 495 | 616 | -121 |
| 1998-08-06 | @ MIN | 113 | W 8-7 | 52-61 | 2 | 14,332 | Jose Rosado | Dan Serafini | Scott Service | Rick Aguilera | Jeff Montgomery | 503 | 623 | -120 |
| 1998-08-07 | @ NYA | 114 | L 2-8 | 52-63 | 2 | 14,425 | Pat Rapp | David Cone | David Cone | Pat Rapp | | 505 | 631 | -126 |
| 1998-08-07 | @ NYA | 115 | L 2-14 | 52-63 | 2 | 37,988 | Chris Haney | David Wells | David Wells | Chris Haney | | 507 | 645 | -138 |
| 1998-08-08 | @ NYA | 116 | L 1-14 | 52-64 | 3 | 45,975 | Glendon Rusch | Orlando Hernandez | Orlando Hernandez | Glendon Rusch | | 508 | 659 | -151 |
| 1998-08-09 | @ NYA | 117 | L 4-5 | 52-65 | 4 | 55,911 | Hipolito Pichardo | Andy Pettitte | Ramiro Mendoza | Scott Service | Mariano Rivera | 512 | 664 | -152 |
| 1998-08-11 | @ BOS | 118 | L 4-7 | 52-66 | 4 | 33,290 | Tim Belcher | Steve Avery | Tom Gordon | Jeff Montgomery | | 516 | 671 | -155 |
| 1998-08-12 | @ BOS | 119 | W 8-4 | 53-66 | 3 | 32,488 | Jose Rosado | Bret Saberhagen | Scott Service | Greg Swindell | | 524 | 675 | -151 |
| 1998-08-13 | vs TBA | 120 | W 6-4 | 54-66 | 3 | 18,289 | Pat Rapp | Bryan Rekar | Jeff Montgomery | Roberto Hernandez | | 530 | 679 | -149 |
| 1998-08-14 | vs TBA | 121 | W 11-9 | 55-66 | 3 | 28,133 | Chris Haney | Rolando Arrojo | Chris Haney | Rolando Arrojo | Scott Service | 541 | 688 | -147 |
| 1998-08-15 | vs TBA | 122 | L 6-8 | 55-67 | 3 | 18,706 | Hipolito Pichardo | Tony Saunders | Jim Mecir | Ricky Bones | Roberto Hernandez | 547 | 696 | -149 |
| 1998-08-16 | vs TBA | 123 | L 3-8 | 55-68 | 3 | 16,762 | Tim Belcher | Julio Santana | Julio Santana | Tim Belcher | | 550 | 704 | -154 |
| 1998-08-17 | vs NYA | 124 | L 1-7 | 55-69 | 3 | 27,895 | Jose Rosado | David Cone | David Cone | Jose Rosado | | 551 | 711 | -160 |
| 1998-08-18 | vs NYA | 125 | L 2-3 | 55-70 | 3 | 26,259 | Pat Rapp | Orlando Hernandez | Joe Borowski | Matt Whisenant | | 553 | 714 | -161 |
| 1998-08-19 | vs BOS | 126 | L 1-11 | 55-71 | 4 | 14,017 | Brian Barber | Tim Wakefield | Tim Wakefield | Brian Barber | | 554 | 725 | -171 |
| 1998-08-20 | vs BOS | 127 | W 8-2 | 56-71 | 4 | 14,278 | Hipolito Pichardo | Pete Schourek | Hipolito Pichardo | Pete Schourek | | 562 | 727 | -165 |
| 1998-08-21 | @ TBA | 128 | W 6-5 | 57-71 | 3 | 25,368 | Tim Belcher | Julio Santana | Matt Whisenant | Esteban Yan | Jeff Montgomery | 568 | 732 | -164 |
| 1998-08-22 | @ TBA | 129 | W 3-2 | 58-71 | 2 | 27,346 | Jose Rosado | Wilson Alvarez | Jose Rosado | Wilson Alvarez | Jeff Montgomery | 571 | 734 | -163 |
| 1998-08-23 | @ TBA | 130 | W 11-5 | 59-71 | 2 | 33,123 | Pat Rapp | Bryan Rekar | Pat Rapp | Bryan Rekar | | 582 | 739 | -157 |
| 1998-08-24 | @ TOR | 131 | W 7-3 | 60-71 | 2 | 26,306 | Brian Barber | Pat Hentgen | Brian Barber | Pat Hentgen | Matt Whisenant | 589 | 742 | -153 |
| 1998-08-25 | @ TOR | 132 | L 0-3 | 60-72 | 2 | 26,173 | Chris Haney | Roger Clemens | Roger Clemens | Chris Haney | | 589 | 745 | -156 |
| 1998-08-26 | @ TOR | 133 | W 7-2 | 61-72 | 2 | 25,557 | Tim Belcher | Chris Carpenter | Tim Belcher | Chris Carpenter | | 596 | 747 | -151 |
| 1998-08-27 | @ TOR | 134 | L 1-11 | 61-73 | 2 | 25,524 | Jose Rosado | Kelvim Escobar | Kelvim Escobar | Jose Rosado | | 597 | 758 | -161 |
| 1998-08-28 | @ BAL | 135 | W 6-5 | 62-73 | 2 | 47,530 | Pat Rapp | Sidney Ponson | Pat Rapp | Sidney Ponson | Jeff Montgomery | 603 | 763 | -160 |
| 1998-08-29 | @ BAL | 136 | W 2-1 | 63-73 | 2 | 48,154 | Brian Barber | Mike Mussina | Brian Barber | Mike Mussina | Jeff Montgomery | 605 | 764 | -159 |
| 1998-08-30 | @ BAL | 137 | W 3-2 | 64-73 | 2 | 47,838 | Chris Haney | Juan Guzman | Chris Haney | Juan Guzman | Jeff Montgomery | 608 | 766 | -158 |
| 1998-09-01 | vs TOR | 138 | L 1-2 | 64-74 | 2 | 12,447 | Tim Belcher | Chris Carpenter | Chris Carpenter | Tim Belcher | Paul Quantrill | 609 | 768 | -159 |
| 1998-09-02 | vs TOR | 139 | L 0-5 | 64-75 | 3 | 12,541 | Jose Rosado | Kelvim Escobar | Kelvim Escobar | Jose Rosado | Paul Quantrill | 609 | 773 | -164 |
| 1998-09-04 | @ ANA | 140 | W 5-3 | 65-75 | 2 | 33,832 | Pat Rapp | Ken Hill | Ricky Bones | Mike Holtz | Jeff Montgomery | 614 | 776 | -162 |
| 1998-09-05 | @ ANA | 141 | L 1-2 | 65-76 | 3 | 37,217 | Brian Barber | Jack McDowell | Jack McDowell | Brian Barber | Rich DeLucia | 615 | 778 | -163 |
| 1998-09-06 | @ ANA | 142 | L 0-3 | 65-77 | 3 | 33,941 | Tim Belcher | Chuck Finley | Chuck Finley | Tim Belcher | Shigetoshi Hasegawa | 615 | 781 | -166 |
| 1998-09-08 | @ TEX | 143 | L 6-7 | 65-78 | 3 | 22,336 | Jose Rosado | John Burkett | Danny Patterson | Jeff Montgomery | | 621 | 788 | -167 |
| 1998-09-09 | @ TEX | 144 | L 0-8 | 65-79 | 3 | 28,441 | Pat Rapp | Aaron Sele | Aaron Sele | Pat Rapp | | 621 | 796 | -175 |
| 1998-09-11 | vs SEA | 145 | L 3-6 | 66-80 | 3 | 0 | Brian Barber | Jeff Fassero | Jeff Fassero | Brian Barber | Mike Timlin | 624 | 802 | -178 |
| 1998-09-11 | vs SEA | 146 | W 8-5 | 66-80 | 3 | 18,874 | Kevin Appier | Ken Cloude | Kevin Appier | Bill Swift | Glendon Rusch | 632 | 807 | -175 |
| 1998-09-12 | vs SEA | 147 | W 5-2 | 67-80 | 3 | 28,091 | Tim Belcher | Jamie Moyer | Tim Belcher | Jamie Moyer | Jeff Montgomery | 637 | 809 | -172 |
| 1998-09-14 | vs OAK | 148 | W 16-6 | 68-80 | 3 | 12,103 | Jose Rosado | Jimmy Haynes | Ricky Bones | Blake Stein | Scott Service | 653 | 815 | -162 |
| 1998-09-15 | vs OAK | 149 | W 6-3 | 69-80 | 3 | 11,524 | Pat Rapp | Kenny Rogers | Pat Rapp | Kenny Rogers | Jeff Montgomery | 659 | 818 | -159 |
| 1998-09-16 | @ CHA | 150 | L 4-9 | 69-81 | 3 | 12,894 | Brian Barber | Jim Abbott | Jim Abbott | Brian Bevil | | 663 | 827 | -164 |
| 1998-09-17 | @ CHA | 151 | W 13-4 | 70-81 | 3 | 13,552 | Tim Belcher | James Baldwin | Tim Belcher | James Baldwin | | 676 | 831 | -155 |
| 1998-09-18 | @ CLE | 152 | L 1-4 | 70-82 | 3 | 43,260 | Kevin Appier | Jaret Wright | Jaret Wright | Kevin Appier | Paul Shuey | 677 | 835 | -158 |
| 1998-09-19 | @ CLE | 153 | W 7-6 | 71-82 | 3 | 43,182 | Jose Rosado | Dwight Gooden | Scott Service | Paul Shuey | Jeff Montgomery | 684 | 841 | -157 |
| 1998-09-20 | @ CLE | 154 | L 3-5 | 71-83 | 3 | 43,082 | Pat Rapp | Bartolo Colon | Bartolo Colon | Pat Rapp | Michael Jackson | 687 | 846 | -159 |
| 1998-09-21 | vs DET | 155 | L 5-7 | 71-84 | 3 | 10,990 | Brian Barber | Brian Powell | Dean Crow | Scott Service | Todd Jones | 692 | 853 | -161 |
| 1998-09-22 | vs DET | 156 | L 4-14 | 71-85 | 3 | 11,871 | Tim Belcher | Justin Thompson | Justin Thompson | Tim Belcher | Frank Castillo | 696 | 867 | -171 |
| 1998-09-23 | vs DET | 157 | L 1-5 | 71-86 | 3 | 12,100 | Kevin Appier | Bryce Florie | Bryce Florie | Kevin Appier | | 697 | 872 | -175 |
| 1998-09-24 | vs CHA | 158 | W 6-4 | 72-86 | 3 | 13,481 | Jose Rosado | Jaime Navarro | Jose Rosado | Jaime Navarro | Jeff Montgomery | 703 | 876 | -173 |
| 1998-09-25 | vs CHA | 159 | L 0-3 | 72-87 | 3 | 16,683 | Jeff Suppan | Mike Sirotka | Mike Sirotka | Ricky Bones | Bob Howry | 703 | 879 | -176 |
| 1998-09-26 | vs CHA | 160 | L 5-13 | 72-88 | 3 | 21,846 | Brian Barber | Jim Abbott | Jim Abbott | Brian Barber | | 708 | 892 | -184 |
| 1998-09-27 | vs CHA | 161 | L 6-7 | 72-89 | 3 | 13,578 | Tim Belcher | James Baldwin | James Baldwin | Tim Belcher | Bob Howry | 714 | 899 | -185 |