Bill Swift had a record of 41-49 with an ERA of 4.33, 369 strikeouts and 24 saves in 282 appearances for the Mariners in his career.
| NAME | SEASON | TM | G | W | L | W% | GS | ERA | SO | CG | SHO | SV | IP | H | ER | R | HR | BB | HBP | GF | IBB | TBF | WP | K/9 | BB/9 | K/BB | HR/9 | K% | BB% | WHIP | BABIP | RA | ERA- | FIP | FIP- | H/9 | PRAA | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 |  | B. Swift | 1985 |  SEA | 23 | 6 | 10 | .375 | 21 | 4.77 | 55 | 0 | 0 | 0 | 120.2 | 131 | 64 | 71 | 8 | 48 | 5 | 0 | 5 | 532 | 5 | 4.10 | 3.58 | 1.15 | 0.60 | 10.3 | 9.0 | 1.48 | .296 | 5.30 | 114 | 3.95 | 93 | 9.77 | 4.1 |
| 2 | | B. Swift | 1986 | SEA | 29 | 2 | 9 | .182 | 17 | 5.46 | 55 | 1 | 0 | 0 | 115.1 | 148 | 70 | 85 | 5 | 55 | 7 | 3 | 2 | 534 | 2 | 4.29 | 4.29 | 1.00 | 0.39 | 10.3 | 10.3 | 1.76 | .347 | 6.63 | 127 | 3.98 | 91 | 11.55 | 4.9 |
| 3 | | B. Swift | 1988 |  SEA | 38 | 8 | 12 | .400 | 24 | 4.59 | 47 | 6 | 1 | 0 | 174.2 | 199 | 89 | 99 | 10 | 65 | 8 | 4 | 3 | 757 | 6 | 2.42 | 3.35 | 0.72 | 0.52 | 6.2 | 8.6 | 1.51 | .301 | 5.10 | 111 | 4.22 | 103 | 10.25 | -1.6 |
| 4 | | B. Swift | 1989 | SEA | 37 | 7 | 3 | .700 | 16 | 4.43 | 45 | 0 | 0 | 1 | 130.0 | 140 | 64 | 72 | 7 | 38 | 2 | 7 | 4 | 551 | 4 | 3.12 | 2.63 | 1.18 | 0.48 | 8.2 | 6.9 | 1.37 | .290 | 4.98 | 111 | 3.69 | 94 | 9.69 | 3.3 |
| 5 | | B. Swift | 1990 | SEA | 55 | 6 | 4 | .600 | 8 | 2.39 | 42 | 0 | 0 | 6 | 128.0 | 135 | 34 | 46 | 4 | 21 | 7 | 18 | 6 | 533 | 8 | 2.95 | 1.48 | 2.00 | 0.28 | 7.9 | 3.9 | 1.22 | .285 | 3.23 | 60 | 3.21 | 80 | 9.49 | 11 |
| 6 | | B. Swift | 1991 | SEA | 71 | 1 | 2 | .333 | 0 | 1.99 | 48 | 0 | 0 | 17 | 90.1 | 74 | 20 | 22 | 3 | 26 | 1 | 30 | 4 | 359 | 2 | 4.78 | 2.59 | 1.85 | 0.30 | 13.4 | 7.2 | 1.11 | .253 | 2.19 | 48 | 3.12 | 77 | 7.37 | 9.3 |
| 7 | | B. Swift | 1998 |  SEA | 29 | 11 | 9 | .550 | 26 | 5.85 | 77 | 0 | 0 | 0 | 144.2 | 183 | 94 | 103 | 21 | 51 | 10 | 0 | 2 | 663 | 1 | 4.79 | 3.17 | 1.51 | 1.31 | 11.6 | 7.7 | 1.62 | .321 | 6.41 | 126 | 5.22 | 113 | 11.38 | -9.6 |
| Total | 282 | 41 | 49 | .456 | 112 | 4.33 | 369 | 7 | 1 | 24 | 903.2 | 1,010 | 435 | 498 | 58 | 304 | 40 | 62 | 26 | 3,929 | 28 | 3.68 | 3.03 | 1.21 | 0.58 | 9.4 | 7.7 | 1.45 | .301 | 4.96 | 102 | 3.98 | 95 | 10.06 | 21.5 |
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