| 1998-03-31 | vs KCA | 1 | L 1-4 | 0-1 | 1 | 46,820 | Mike Mussina | Tim Belcher | Tim Belcher | Mike Mussina | Jeff Montgomery | 1 | 4 | -3 |
| 1998-04-01 | vs KCA | 2 | W 10-1 | 1-1 | 3 | 38,623 | Scott Erickson | Glendon Rusch | Scott Erickson | Glendon Rusch | | 11 | 5 | 6 |
| 1998-04-02 | vs KCA | 3 | W 4-3 | 2-1 | 2 | 39,435 | Jimmy Key | Pat Rapp | Armando Benitez | Jeff Montgomery | | 15 | 8 | 7 |
| 1998-04-03 | vs DET | 4 | W 10-2 | 3-1 | 1 | 39,364 | Doug Drabek | Scott Sanders | Doug Drabek | Scott Sanders | | 25 | 10 | 15 |
| 1998-04-04 | vs DET | 5 | W 2-1 | 4-1 | 1 | 43,306 | Scott Kamieniecki | Greg Keagle | Scott Kamieniecki | Greg Keagle | Armando Benitez | 27 | 11 | 16 |
| 1998-04-05 | vs DET | 6 | W 6-3 | 5-1 | 1 | 40,967 | Mike Mussina | Justin Thompson | Mike Mussina | Justin Thompson | Jesse Orosco | 33 | 14 | 19 |
| 1998-04-07 | @ KCA | 7 | W 11-7 | 6-1 | 1 | 40,419 | Scott Erickson | Glendon Rusch | Scott Erickson | Glendon Rusch | | 44 | 21 | 23 |
| 1998-04-09 | @ KCA | 8 | W 2-1 | 7-1 | 1 | 13,790 | Jimmy Key | Pat Rapp | Jimmy Key | Jose Rosado | Armando Benitez | 46 | 22 | 24 |
| 1998-04-10 | @ DET | 9 | L 1-7 | 7-2 | 1 | 13,786 | Doug Drabek | Tim Worrell | Tim Worrell | Doug Drabek | | 47 | 29 | 18 |
| 1998-04-11 | @ DET | 10 | W 2-0 | 8-2 | 1 | 22,094 | Mike Mussina | Justin Thompson | Mike Mussina | Justin Thompson | Armando Benitez | 49 | 29 | 20 |
| 1998-04-12 | @ DET | 11 | W 6-3 | 9-2 | 1 | 11,183 | Scott Erickson | Greg Keagle | Scott Erickson | Greg Keagle | Armando Benitez | 55 | 32 | 23 |
| 1998-04-14 | vs CHA | 12 | W 4-3 | 10-2 | 1 | 43,039 | Jimmy Key | Scott Eyre | Jimmy Key | Scott Eyre | Jesse Orosco | 59 | 35 | 24 |
| 1998-04-15 | vs CHA | 13 | L 6-7 | 10-3 | 1 | 46,546 | Doug Drabek | James Baldwin | James Baldwin | Doug Drabek | Matt Karchner | 65 | 42 | 23 |
| 1998-04-16 | vs CHA | 14 | L 2-8 | 10-4 | 1 | 48,093 | Mike Mussina | Mike Sirotka | Mike Sirotka | Mike Mussina | | 67 | 50 | 17 |
| 1998-04-17 | @ TEX | 15 | L 4-6 | 10-5 | 1 | 37,415 | Scott Erickson | Darren Oliver | Roger Pavlik | Scott Erickson | John Wetteland | 71 | 56 | 15 |
| 1998-04-18 | @ TEX | 16 | W 10-8 | 11-5 | 2 | 43,883 | Scott Kamieniecki | John Burkett | Scott Kamieniecki | John Burkett | | 81 | 64 | 17 |
| 1998-04-19 | @ TEX | 17 | L 7-11 | 11-6 | 1 | 43,037 | Jimmy Key | Bobby Witt | Bobby Witt | Jimmy Key | John Wetteland | 88 | 75 | 13 |
| 1998-04-20 | @ ANA | 18 | L 3-4 | 11-7 | 4 | 19,217 | Doug Drabek | Ken Hill | Ken Hill | Doug Drabek | Troy Percival | 91 | 79 | 12 |
| 1998-04-21 | @ ANA | 19 | W 8-3 | 12-7 | 3 | 20,968 | Doug Johns | Jack McDowell | Arthur Rhodes | Jack McDowell | | 99 | 82 | 17 |
| 1998-04-22 | @ ANA | 20 | L 6-7 | 12-8 | 3 | 22,739 | Scott Erickson | Chuck Finley | Mike Holtz | Terry Mathews | Troy Percival | 105 | 89 | 16 |
| 1998-04-24 | vs OAK | 21 | L 1-10 | 12-9 | 3 | 47,411 | Scott Kamieniecki | Kenny Rogers | Kenny Rogers | Scott Kamieniecki | | 106 | 99 | 7 |
| 1998-04-25 | vs OAK | 22 | W 8-2 | 13-9 | 3 | 46,026 | Jimmy Key | Jimmy Haynes | Jimmy Key | Jimmy Haynes | | 114 | 101 | 13 |
| 1998-04-26 | vs OAK | 23 | L 4-12 | 13-10 | 3 | 43,339 | Doug Drabek | Tom Candiotti | Tom Candiotti | Doug Drabek | | 118 | 113 | 5 |
| 1998-04-27 | vs ANA | 24 | L 1-3 | 13-11 | 3 | 42,961 | Scott Erickson | Chuck Finley | Chuck Finley | Scott Erickson | Troy Percival | 119 | 116 | 3 |
| 1998-04-28 | vs ANA | 25 | L 5-6 | 13-12 | 3 | 41,877 | Nerio Rodriguez | Jason Dickson | Jason Dickson | Nerio Rodriguez | Troy Percival | 124 | 122 | 2 |
| 1998-04-29 | @ CHA | 26 | L 7-16 | 13-13 | 3 | 12,262 | Sidney Ponson | Jaime Navarro | Jaime Navarro | Sidney Ponson | | 131 | 138 | -7 |
| 1998-04-30 | @ CHA | 27 | W 4-1 | 14-13 | 3 | 11,772 | Jimmy Key | Scott Eyre | Jimmy Key | Scott Eyre | Armando Benitez | 135 | 139 | -4 |
| 1998-05-01 | vs MIN | 28 | W 6-3 | 15-13 | 3 | 43,233 | Doug Drabek | Brad Radke | Doug Drabek | Brad Radke | Armando Benitez | 141 | 142 | -1 |
| 1998-05-02 | vs MIN | 29 | L 7-8 | 15-14 | 3 | 45,237 | Scott Erickson | Mike Morgan | Rick Aguilera | Doug Johns | | 148 | 150 | -2 |
| 1998-05-03 | vs MIN | 30 | W 2-0 | 16-14 | 3 | 43,930 | Mike Mussina | Eric Milton | Mike Mussina | Eric Milton | Arthur Rhodes | 150 | 150 | 0 |
| 1998-05-05 | @ CLE | 31 | L 5-6 | 16-15 | 3 | 40,706 | Jimmy Key | Jaret Wright | Paul Assenmacher | Armando Benitez | | 155 | 156 | -1 |
| 1998-05-06 | @ CLE | 32 | L 5-14 | 16-16 | 3 | 40,672 | Scott Erickson | Dave Burba | Dave Burba | Scott Erickson | | 160 | 170 | -10 |
| 1998-05-08 | @ TBA | 33 | W 8-2 | 17-16 | 3 | 35,355 | Doug Drabek | Tony Saunders | Arthur Rhodes | Albie Lopez | | 168 | 172 | -4 |
| 1998-05-09 | @ TBA | 34 | W 7-0 | 18-16 | 3 | 42,486 | Mike Mussina | Dennis Springer | Mike Mussina | Dennis Springer | | 175 | 172 | 3 |
| 1998-05-10 | @ TBA | 35 | L 3-4 | 18-17 | 3 | 34,123 | Jimmy Key | Wilson Alvarez | Esteban Yan | Alan Mills | Roberto Hernandez | 178 | 176 | 2 |
| 1998-05-11 | @ MIN | 36 | W 4-0 | 19-17 | 3 | 9,317 | Scott Erickson | Bob Tewksbury | Scott Erickson | Bob Tewksbury | | 182 | 176 | 6 |
| 1998-05-12 | @ MIN | 37 | L 4-7 | 19-18 | 3 | 8,666 | Scott Kamieniecki | LaTroy Hawkins | LaTroy Hawkins | Arthur Rhodes | Rick Aguilera | 186 | 183 | 3 |
| 1998-05-13 | vs CLE | 38 | W 8-1 | 20-18 | 3 | 43,379 | Doug Drabek | Chad Ogea | Doug Drabek | Chad Ogea | | 194 | 184 | 10 |
| 1998-05-14 | vs CLE | 39 | L 4-5 | 20-19 | 3 | 43,039 | Mike Mussina | Charles Nagy | Charles Nagy | Arthur Rhodes | Michael Jackson | 198 | 189 | 9 |
| 1998-05-15 | vs TBA | 40 | L 1-4 | 20-20 | 3 | 47,421 | Jimmy Key | Wilson Alvarez | Wilson Alvarez | Jimmy Key | Roberto Hernandez | 199 | 193 | 6 |
| 1998-05-16 | vs TBA | 41 | L 2-5 | 20-21 | 3 | 47,538 | Scott Erickson | Rolando Arrojo | Rolando Arrojo | Scott Erickson | Roberto Hernandez | 201 | 198 | 3 |
| 1998-05-17 | vs TBA | 42 | L 3-7 | 20-22 | 3 | 47,628 | Scott Kamieniecki | Jason Johnson | Jim Mecir | Alan Mills | | 204 | 205 | -1 |
| 1998-05-18 | vs TBA | 43 | L 3-6 | 20-23 | 4 | 45,033 | Doug Drabek | Tony Saunders | Albie Lopez | Doug Drabek | Roberto Hernandez | 207 | 211 | -4 |
| 1998-05-19 | @ NYA | 44 | L 5-9 | 20-24 | 5 | 31,311 | Doug Johns | David Cone | Mike Stanton | Norm Charlton | | 212 | 220 | -8 |
| 1998-05-20 | @ NYA | 45 | L 6-9 | 20-25 | 5 | 32,449 | Jimmy Key | Hideki Irabu | Hideki Irabu | Jimmy Key | | 218 | 229 | -11 |
| 1998-05-21 | @ NYA | 46 | L 1-3 | 20-26 | 5 | 34,588 | Scott Erickson | Andy Pettitte | Andy Pettitte | Scott Erickson | Mariano Rivera | 219 | 232 | -13 |
| 1998-05-22 | @ OAK | 47 | L 5-9 | 20-27 | 5 | 11,035 | Scott Kamieniecki | Tom Candiotti | Tom Candiotti | Scott Kamieniecki | | 224 | 241 | -17 |
| 1998-05-23 | @ OAK | 48 | W 9-1 | 21-27 | 5 | 26,419 | Doug Drabek | Jimmy Haynes | Doug Drabek | Jimmy Haynes | | 233 | 242 | -9 |
| 1998-05-24 | @ OAK | 49 | W 2-1 | 22-27 | 5 | 23,187 | Doug Johns | Kenny Rogers | Jesse Orosco | Billy Taylor | Sidney Ponson | 235 | 243 | -8 |
| 1998-05-25 | @ SEA | 50 | L 4-12 | 22-28 | 5 | 28,375 | Nerio Rodriguez | Bill Swift | Bill Swift | Nerio Rodriguez | | 239 | 255 | -16 |
| 1998-05-26 | @ SEA | 51 | W 8-3 | 23-28 | 5 | 31,164 | Scott Erickson | Jeff Fassero | Scott Erickson | Jeff Fassero | | 247 | 258 | -11 |
| 1998-05-28 | vs TEX | 52 | W 5-2 | 24-28 | 4 | 42,294 | Doug Drabek | Bobby Witt | Doug Drabek | Bobby Witt | Jesse Orosco | 252 | 260 | -8 |
| 1998-05-29 | vs TEX | 53 | W 6-3 | 25-28 | 4 | 47,091 | Doug Johns | Aaron Sele | Doug Johns | Aaron Sele | Armando Benitez | 258 | 263 | -5 |
| 1998-05-30 | vs TEX | 54 | L 8-10 | 25-29 | 4 | 47,866 | Bobby Munoz | Rick Helling | Xavier Hernandez | Sidney Ponson | John Wetteland | 266 | 273 | -7 |
| 1998-05-31 | vs TEX | 55 | L 5-9 | 25-30 | 4 | 47,437 | Scott Erickson | Darren Oliver | Darren Oliver | Scott Erickson | Danny Patterson | 271 | 282 | -11 |
| 1998-06-01 | vs SEA | 56 | W 10-9 | 26-30 | 4 | 42,622 | Richie Lewis | Jeff Fassero | Alan Mills | Tony Fossas | Armando Benitez | 281 | 291 | -10 |
| 1998-06-02 | vs SEA | 57 | W 9-8 | 27-30 | 4 | 46,724 | Doug Drabek | Jamie Moyer | Norm Charlton | Bobby Ayala | | 290 | 299 | -9 |
| 1998-06-03 | @ BOS | 58 | W 3-0 | 28-30 | 4 | 31,355 | Doug Johns | Derek Lowe | Doug Johns | Derek Lowe | Arthur Rhodes | 293 | 299 | -6 |
| 1998-06-04 | @ BOS | 59 | L 1-9 | 28-31 | 4 | 33,104 | Sidney Ponson | Bret Saberhagen | Bret Saberhagen | Sidney Ponson | | 294 | 308 | -14 |
| 1998-06-05 | vs ATL | 60 | W 3-2 | 29-31 | 4 | 48,039 | Scott Erickson | Denny Neagle | Scott Erickson | Denny Neagle | | 297 | 310 | -13 |
| 1998-06-06 | vs ATL | 61 | L 5-10 | 29-32 | 4 | 48,098 | Mike Mussina | Kevin Millwood | Kevin Millwood | Mike Mussina | | 302 | 320 | -18 |
| 1998-06-07 | vs ATL | 62 | L 0-9 | 29-33 | 4 | 48,090 | Doug Drabek | Greg Maddux | Greg Maddux | Doug Drabek | | 302 | 329 | -27 |
| 1998-06-08 | @ PHI | 63 | W 14-8 | 30-33 | 4 | 26,742 | Doug Johns | Mike Grace | Arthur Rhodes | Darrin Winston | Jesse Orosco | 316 | 337 | -21 |
| 1998-06-09 | @ PHI | 64 | L 0-2 | 30-34 | 4 | 27,602 | Sidney Ponson | Matt Beech | Matt Beech | Sidney Ponson | Mark Leiter | 316 | 339 | -23 |
| 1998-06-10 | @ PHI | 65 | W 5-2 | 31-34 | 4 | 27,326 | Scott Erickson | Tyler Green | Armando Benitez | Mark Leiter | | 321 | 341 | -20 |
| 1998-06-12 | @ TOR | 66 | W 9-5 | 32-34 | 3 | 30,237 | Mike Mussina | Juan Guzman | Mike Mussina | Juan Guzman | | 330 | 346 | -16 |
| 1998-06-13 | @ TOR | 67 | L 8-9 | 32-35 | 4 | 38,102 | Doug Drabek | Chris Carpenter | Robert Person | Doug Drabek | Randy Myers | 338 | 355 | -17 |
| 1998-06-14 | @ TOR | 68 | L 4-7 | 32-36 | 4 | 28,132 | Pete Smith | Roger Clemens | Roger Clemens | Pete Smith | Randy Myers | 342 | 362 | -20 |
| 1998-06-15 | vs NYA | 69 | W 7-4 | 33-36 | 4 | 48,022 | Scott Erickson | David Wells | Scott Erickson | David Wells | Jesse Orosco | 349 | 366 | -17 |
| 1998-06-16 | vs NYA | 70 | W 2-0 | 34-36 | 3 | 48,027 | Sidney Ponson | Hideki Irabu | Sidney Ponson | Hideki Irabu | Arthur Rhodes | 351 | 366 | -15 |
| 1998-06-17 | vs NYA | 71 | L 3-5 | 34-37 | 3 | 48,269 | Mike Mussina | Andy Pettitte | Andy Pettitte | Mike Mussina | Mariano Rivera | 354 | 371 | -17 |
| 1998-06-18 | vs TOR | 72 | L 6-13 | 34-38 | 4 | 47,374 | Doug Johns | Chris Carpenter | Chris Carpenter | Doug Johns | | 360 | 384 | -24 |
| 1998-06-19 | vs TOR | 73 | W 7-4 | 35-38 | 3 | 47,012 | Pete Smith | Roger Clemens | Norm Charlton | Bill Risley | | 367 | 388 | -21 |
| 1998-06-20 | vs TOR | 74 | W 11-3 | 36-38 | 3 | 48,011 | Scott Erickson | Woody Williams | Scott Erickson | Woody Williams | | 378 | 391 | -13 |
| 1998-06-21 | vs TOR | 75 | L 3-7 | 36-39 | 3 | 47,522 | Sidney Ponson | Pat Hentgen | Pat Hentgen | Sidney Ponson | Randy Myers | 381 | 398 | -17 |
| 1998-06-22 | vs NYN | 76 | W 7-2 | 37-39 | 3 | 45,535 | Mike Mussina | Bobby Jones | Mike Mussina | Bobby Jones | | 388 | 400 | -12 |
| 1998-06-23 | vs NYN | 77 | L 3-6 | 37-40 | 4 | 46,385 | Doug Johns | Masato Yoshii | John Hudek | Arthur Rhodes | John Franco | 391 | 406 | -15 |
| 1998-06-24 | @ NYN | 78 | L 3-6 | 37-41 | 4 | 29,789 | Pete Smith | Rick Reed | Rick Reed | Pete Smith | John Franco | 394 | 412 | -18 |
| 1998-06-25 | @ NYN | 79 | L 2-3 | 37-42 | 4 | 35,156 | Scott Erickson | Hideo Nomo | Dennis Cook | Armando Benitez | | 396 | 415 | -19 |
| 1998-06-26 | @ MON | 80 | L 4-9 | 37-43 | 4 | 9,116 | Sidney Ponson | Dustin Hermanson | Dustin Hermanson | Sidney Ponson | | 400 | 424 | -24 |
| 1998-06-27 | @ MON | 81 | L 1-3 | 37-44 | 4 | 11,556 | Mike Mussina | Carl Pavano | Carl Pavano | Mike Mussina | Ugueth Urbina | 401 | 427 | -26 |
| 1998-06-28 | @ MON | 82 | L 4-8 | 37-45 | 4 | 16,145 | Doug Drabek | Javier Vazquez | Javier Vazquez | Doug Drabek | Ugueth Urbina | 405 | 435 | -30 |
| 1998-06-30 | vs FLO | 83 | L 5-7 | 37-46 | 4 | 43,505 | Scott Erickson | Brian Meadows | Brian Edmondson | Alan Mills | Matt Mantei | 410 | 442 | -32 |
| 1998-07-01 | vs FLO | 84 | L 3-5 | 37-47 | 4 | 41,997 | Pete Smith | Livan Hernandez | Livan Hernandez | Pete Smith | Jay Powell | 413 | 447 | -34 |
| 1998-07-02 | vs FLO | 85 | W 5-3 | 38-47 | 4 | 46,006 | Sidney Ponson | Joe Fontenot | Sidney Ponson | Joe Fontenot | Armando Benitez | 418 | 450 | -32 |
| 1998-07-03 | @ NYA | 86 | L 2-3 | 38-48 | 4 | 43,328 | Mike Mussina | Andy Pettitte | Andy Pettitte | Jesse Orosco | | 420 | 453 | -33 |
| 1998-07-04 | @ NYA | 87 | L 3-4 | 38-49 | 4 | 37,390 | Doug Drabek | Orlando Hernandez | Orlando Hernandez | Doug Drabek | Mariano Rivera | 423 | 457 | -34 |
| 1998-07-05 | @ NYA | 88 | L 0-1 | 38-50 | 4 | 52,506 | Scott Erickson | David Cone | David Cone | Scott Erickson | Mariano Rivera | 423 | 458 | -35 |
| 1998-07-09 | vs BOS | 89 | W 3-2 | 39-50 | 4 | 48,014 | Mike Mussina | Bret Saberhagen | Jesse Orosco | Jim Corsi | Armando Benitez | 426 | 460 | -34 |
| 1998-07-10 | vs BOS | 90 | W 3-2 | 40-50 | 4 | 48,043 | Sidney Ponson | Pedro Martinez | Jesse Orosco | Pedro Martinez | Armando Benitez | 429 | 462 | -33 |
| 1998-07-11 | vs BOS | 91 | W 2-1 | 41-50 | 4 | 48,244 | Scott Erickson | Tim Wakefield | Scott Erickson | Tim Wakefield | Jesse Orosco | 431 | 463 | -32 |
| 1998-07-12 | vs BOS | 92 | W 11-7 | 42-50 | 4 | 48,193 | Doug Drabek | Jin Ho Cho | Doug Johns | Jin Ho Cho | Alan Mills | 442 | 470 | -28 |
| 1998-07-13 | vs TOR | 93 | W 5-0 | 43-50 | 4 | 41,474 | Nerio Rodriguez | Juan Guzman | Nerio Rodriguez | Juan Guzman | | 447 | 470 | -23 |
| 1998-07-14 | vs TOR | 94 | W 11-5 | 44-50 | 4 | 44,122 | Mike Mussina | Woody Williams | Mike Mussina | Woody Williams | | 458 | 475 | -17 |
| 1998-07-15 | @ TEX | 95 | W 14-3 | 45-50 | 4 | 46,682 | Sidney Ponson | Rick Helling | Sidney Ponson | Rick Helling | | 472 | 478 | -6 |
| 1998-07-16 | @ TEX | 96 | W 9-3 | 46-50 | 4 | 45,171 | Scott Erickson | Aaron Sele | Scott Erickson | Aaron Sele | | 481 | 481 | 0 |
| 1998-07-17 | @ ANA | 97 | W 4-1 | 47-50 | 4 | 34,618 | Doug Drabek | Jason Dickson | Doug Drabek | Jason Dickson | Armando Benitez | 485 | 482 | 3 |
| 1998-07-18 | @ ANA | 98 | L 3-8 | 47-51 | 4 | 37,806 | Nerio Rodriguez | Jarrod Washburn | Jarrod Washburn | Nerio Rodriguez | | 488 | 490 | -2 |
| 1998-07-19 | @ ANA | 99 | W 7-4 | 48-51 | 4 | 38,840 | Mike Mussina | Omar Olivares | Jesse Orosco | Troy Percival | | 495 | 494 | 1 |
| 1998-07-21 | vs OAK | 100 | W 7-1 | 49-51 | 4 | 42,174 | Scott Erickson | Tom Candiotti | Scott Erickson | Tom Candiotti | | 502 | 495 | 7 |
| 1998-07-22 | vs OAK | 101 | W 5-4 | 50-51 | 4 | 40,840 | Sidney Ponson | Blake Stein | Armando Benitez | Mike Fetters | | 507 | 499 | 8 |
| 1998-07-23 | vs OAK | 102 | W 9-7 | 51-51 | 3 | 42,371 | Doug Drabek | Jimmy Haynes | Armando Benitez | Mike Fetters | | 516 | 506 | 10 |
| 1998-07-24 | vs SEA | 103 | W 7-4 | 52-51 | 3 | 48,184 | Mike Mussina | Bill Swift | Mike Mussina | Bill Swift | Armando Benitez | 523 | 510 | 13 |
| 1998-07-25 | vs SEA | 104 | L 2-4 | 52-52 | 3 | 48,365 | Scott Kamieniecki | Jeff Fassero | Jeff Fassero | Scott Kamieniecki | Mike Timlin | 525 | 514 | 11 |
| 1998-07-26 | vs SEA | 105 | L 4-10 | 52-53 | 3 | 48,199 | Scott Erickson | Jamie Moyer | Jamie Moyer | Scott Erickson | | 529 | 524 | 5 |
| 1998-07-28 | @ DET | 106 | W 6-5 | 53-53 | 3 | 18,422 | Sidney Ponson | Brian Powell | Sidney Ponson | Bryce Florie | Armando Benitez | 535 | 529 | 6 |
| 1998-07-29 | @ DET | 107 | W 14-2 | 54-53 | 3 | 19,607 | Mike Mussina | Frank Castillo | Mike Mussina | Frank Castillo | Doug Johns | 549 | 531 | 18 |
| 1998-07-30 | @ DET | 108 | W 6-4 | 55-53 | 3 | 22,915 | Jimmy Key | Justin Thompson | Pete Smith | Matt Anderson | Armando Benitez | 555 | 535 | 20 |
| 1998-07-31 | @ KCA | 109 | L 6-9 | 55-54 | 3 | 25,007 | Scott Erickson | Jose Rosado | Jose Rosado | Scott Erickson | | 561 | 544 | 17 |
| 1998-08-01 | @ KCA | 110 | L 5-9 | 55-55 | 3 | 35,144 | Scott Kamieniecki | Pat Rapp | Chris Haney | Scott Kamieniecki | | 566 | 553 | 13 |
| 1998-08-02 | @ KCA | 111 | W 9-2 | 56-55 | 3 | 18,910 | Sidney Ponson | Glendon Rusch | Sidney Ponson | Glendon Rusch | | 575 | 555 | 20 |
| 1998-08-04 | vs DET | 112 | W 4-0 | 57-55 | 3 | 47,519 | Mike Mussina | Bryce Florie | Mike Mussina | Bryce Florie | | 579 | 555 | 24 |
| 1998-08-05 | vs DET | 113 | W 6-1 | 58-55 | 3 | 47,733 | Juan Guzman | Justin Thompson | Juan Guzman | Justin Thompson | | 585 | 556 | 29 |
| 1998-08-07 | @ MIN | 114 | W 16-9 | 59-55 | 3 | 13,662 | Scott Erickson | LaTroy Hawkins | Jimmy Key | Travis Miller | | 601 | 565 | 36 |
| 1998-08-08 | @ MIN | 115 | W 6-3 | 60-55 | 3 | 18,396 | Sidney Ponson | Brad Radke | Sidney Ponson | Brad Radke | Jesse Orosco | 607 | 568 | 39 |
| 1998-08-09 | @ MIN | 116 | L 4-5 | 60-56 | 3 | 16,780 | Mike Mussina | Dan Serafini | Dan Serafini | Mike Mussina | Rick Aguilera | 611 | 573 | 38 |
| 1998-08-10 | @ TBA | 117 | W 2-1 | 61-56 | 3 | 26,352 | Juan Guzman | Tony Saunders | Juan Guzman | Tony Saunders | Armando Benitez | 613 | 574 | 39 |
| 1998-08-11 | @ TBA | 118 | L 1-2 | 61-57 | 3 | 26,472 | Scott Kamieniecki | Julio Santana | Jim Mecir | Armando Benitez | | 614 | 576 | 38 |
| 1998-08-12 | @ TBA | 119 | W 7-0 | 62-57 | 3 | 29,211 | Scott Erickson | Wilson Alvarez | Scott Erickson | Wilson Alvarez | | 621 | 576 | 45 |
| 1998-08-13 | @ CLE | 120 | W 7-4 | 63-57 | 3 | 43,217 | Sidney Ponson | Dwight Gooden | Pete Smith | Steve Reed | Armando Benitez | 628 | 580 | 48 |
| 1998-08-14 | @ CLE | 121 | W 15-3 | 64-57 | 3 | 43,169 | Mike Mussina | Charles Nagy | Mike Mussina | Charles Nagy | | 643 | 583 | 60 |
| 1998-08-15 | @ CLE | 122 | W 9-8 | 65-57 | 3 | 43,238 | Juan Guzman | Dave Burba | Armando Benitez | Doug Jones | | 652 | 591 | 61 |
| 1998-08-16 | @ CLE | 123 | L 3-5 | 65-58 | 3 | 43,069 | Scott Kamieniecki | Jaret Wright | Jaret Wright | Scott Kamieniecki | Michael Jackson | 655 | 596 | 59 |
| 1998-08-17 | vs MIN | 124 | W 3-2 | 66-58 | 3 | 46,606 | Scott Erickson | LaTroy Hawkins | Scott Erickson | LaTroy Hawkins | Armando Benitez | 658 | 598 | 60 |
| 1998-08-18 | vs MIN | 125 | W 7-1 | 67-58 | 3 | 44,022 | Sidney Ponson | Brad Radke | Sidney Ponson | Brad Radke | | 665 | 599 | 66 |
| 1998-08-19 | vs TBA | 126 | W 6-4 | 68-58 | 3 | 44,530 | Mike Mussina | Rolando Arrojo | Mike Mussina | Rolando Arrojo | Armando Benitez | 671 | 603 | 68 |
| 1998-08-20 | vs TBA | 127 | L 2-4 | 68-59 | 3 | 44,566 | Juan Guzman | Tony Saunders | Tony Saunders | Arthur Rhodes | Roberto Hernandez | 673 | 607 | 66 |
| 1998-08-21 | vs CLE | 128 | L 3-6 | 68-60 | 3 | 48,374 | Scott Kamieniecki | Jaret Wright | Jaret Wright | Scott Kamieniecki | | 676 | 613 | 63 |
| 1998-08-22 | vs CLE | 129 | W 6-3 | 69-60 | 3 | 48,138 | Scott Erickson | Bartolo Colon | Scott Erickson | Bartolo Colon | | 682 | 616 | 66 |
| 1998-08-23 | vs CLE | 130 | L 1-4 | 69-61 | 3 | 48,272 | Sidney Ponson | Dwight Gooden | Dwight Gooden | Sidney Ponson | Michael Jackson | 683 | 620 | 63 |
| 1998-08-25 | @ CHA | 131 | L 4-6 | 69-62 | 3 | 15,776 | Mike Mussina | Tom Fordham | Chad Bradford | Mike Mussina | | 687 | 626 | 61 |
| 1998-08-26 | @ CHA | 132 | L 5-12 | 69-63 | 3 | 13,511 | Juan Guzman | James Baldwin | James Baldwin | Juan Guzman | | 692 | 638 | 54 |
| 1998-08-27 | @ CHA | 133 | L 4-7 | 69-64 | 3 | 14,241 | Scott Erickson | Jim Parque | Jim Parque | Scott Erickson | Bill Simas | 696 | 645 | 51 |
| 1998-08-28 | vs KCA | 134 | L 5-6 | 69-65 | 3 | 47,530 | Sidney Ponson | Pat Rapp | Pat Rapp | Sidney Ponson | Jeff Montgomery | 701 | 651 | 50 |
| 1998-08-29 | vs KCA | 135 | L 1-2 | 69-66 | 3 | 48,154 | Mike Mussina | Brian Barber | Brian Barber | Mike Mussina | Jeff Montgomery | 702 | 653 | 49 |
| 1998-08-30 | vs KCA | 136 | L 2-3 | 69-67 | 4 | 47,838 | Juan Guzman | Chris Haney | Chris Haney | Juan Guzman | Jeff Montgomery | 704 | 656 | 48 |
| 1998-08-31 | vs CHA | 137 | L 1-4 | 69-68 | 4 | 40,056 | Scott Erickson | James Baldwin | James Baldwin | Scott Erickson | Bob Howry | 705 | 660 | 45 |
| 1998-09-01 | vs CHA | 138 | L 5-9 | 69-69 | 4 | 40,016 | Doug Drabek | Jim Parque | Jim Parque | Doug Drabek | Jaime Navarro | 710 | 669 | 41 |
| 1998-09-02 | vs CHA | 139 | L 2-3 | 69-70 | 4 | 46,123 | Sidney Ponson | John Snyder | John Snyder | Alan Mills | Bob Howry | 712 | 672 | 40 |
| 1998-09-04 | @ SEA | 140 | W 10-1 | 70-70 | 4 | 27,404 | Juan Guzman | Paul Spoljaric | Juan Guzman | Paul Spoljaric | | 722 | 673 | 49 |
| 1998-09-05 | @ SEA | 141 | L 5-6 | 70-71 | 4 | 43,831 | Scott Erickson | Ken Cloude | Greg McCarthy | Armando Benitez | Mike Timlin | 727 | 679 | 48 |
| 1998-09-06 | @ SEA | 142 | W 5-2 | 71-71 | 4 | 30,285 | Mike Mussina | Jeff Fassero | Mike Mussina | Jeff Fassero | Arthur Rhodes | 732 | 681 | 51 |
| 1998-09-07 | @ SEA | 143 | L 1-11 | 71-72 | 4 | 24,229 | Doug Drabek | Jamie Moyer | Jamie Moyer | Doug Drabek | | 733 | 692 | 41 |
| 1998-09-08 | @ OAK | 144 | W 5-2 | 72-72 | 4 | 7,924 | Doug Johns | Gil Heredia | Arthur Rhodes | Gil Heredia | Armando Benitez | 738 | 694 | 44 |
| 1998-09-09 | @ OAK | 145 | W 6-2 | 73-72 | 4 | 9,015 | Juan Guzman | Jimmy Haynes | Juan Guzman | Jimmy Haynes | | 744 | 696 | 48 |
| 1998-09-11 | vs ANA | 146 | W 8-3 | 74-72 | 4 | 46,832 | Scott Erickson | Chuck Finley | Scott Erickson | Chuck Finley | | 752 | 699 | 53 |
| 1998-09-12 | vs ANA | 147 | W 3-2 | 75-72 | 4 | 48,038 | Mike Mussina | Steve Sparks | Alan Mills | Troy Percival | | 755 | 701 | 54 |
| 1998-09-13 | vs ANA | 148 | W 12-7 | 76-72 | 4 | 48,013 | Rocky Coppinger | Jack McDowell | Jimmy Key | Jarrod Washburn | | 767 | 708 | 59 |
| 1998-09-14 | vs TEX | 149 | W 1-0 | 77-72 | 4 | 41,032 | Juan Guzman | Aaron Sele | Alan Mills | Xavier Hernandez | Armando Benitez | 768 | 708 | 60 |
| 1998-09-15 | vs TEX | 150 | L 5-6 | 77-73 | 4 | 41,363 | Chris Fussell | Esteban Loaiza | Tim Crabtree | Armando Benitez | John Wetteland | 773 | 714 | 59 |
| 1998-09-16 | vs BOS | 151 | L 3-4 | 77-74 | 4 | 42,676 | Scott Erickson | Bret Saberhagen | Bret Saberhagen | Scott Erickson | Tom Gordon | 776 | 718 | 58 |
| 1998-09-17 | vs BOS | 152 | L 2-3 | 77-75 | 4 | 44,565 | Mike Mussina | Pete Schourek | Dennis Eckersley | Armando Benitez | Tom Gordon | 778 | 721 | 57 |
| 1998-09-18 | vs NYA | 153 | L 5-15 | 77-76 | 4 | 48,113 | Juan Guzman | David Wells | David Wells | Juan Guzman | | 783 | 736 | 47 |
| 1998-09-19 | vs NYA | 154 | W 5-3 | 78-76 | 4 | 48,044 | Sidney Ponson | David Cone | Sidney Ponson | David Cone | Alan Mills | 788 | 739 | 49 |
| 1998-09-20 | vs NYA | 155 | L 4-5 | 78-77 | 4 | 48,013 | Doug Johns | Orlando Hernandez | Orlando Hernandez | Doug Johns | Mariano Rivera | 792 | 744 | 48 |
| 1998-09-21 | @ TOR | 156 | L 1-3 | 78-78 | 4 | 30,380 | Scott Erickson | Roger Clemens | Roger Clemens | Scott Erickson | Dan Plesac | 793 | 747 | 46 |
| 1998-09-22 | @ TOR | 157 | L 3-7 | 78-79 | 4 | 26,363 | Mike Mussina | Chris Carpenter | Chris Carpenter | Mike Mussina | | 796 | 754 | 42 |
| 1998-09-23 | @ TOR | 158 | L 3-6 | 78-80 | 4 | 28,147 | Juan Guzman | Kelvim Escobar | Kelvim Escobar | Juan Guzman | Robert Person | 799 | 760 | 39 |
| 1998-09-24 | @ BOS | 159 | L 6-9 | 78-81 | 4 | 30,997 | Sidney Ponson | Pedro Martinez | Pedro Martinez | Sidney Ponson | Tom Gordon | 805 | 769 | 36 |
| 1998-09-25 | @ BOS | 160 | L 3-8 | 78-82 | 4 | 32,644 | Chris Fussell | Tim Wakefield | Tim Wakefield | Chris Fussell | | 808 | 777 | 31 |
| 1998-09-26 | @ BOS | 161 | W 5-2 | 79-82 | 4 | 29,226 | Scott Erickson | Bret Saberhagen | Scott Erickson | Bret Saberhagen | Armando Benitez | 813 | 779 | 34 |
| 1998-09-27 | @ BOS | 162 | L 4-6 | 79-83 | 4 | 32,158 | Mike Mussina | Pete Schourek | Carlos Valdez | Mike Mussina | Tom Gordon | 817 | 785 | 32 |