Mason Miller has the highest career K/9 by a relief pitcher when pitching at least 200 innings, with 15.23 per nine innings.
| NAME | K/9 | IP | G | W | L | W% | GS | ERA | SO | CG | SHO | SV | H | ER | R | HR | BB | HBP | GF | IBB | TBF | WP | BB/9 | K/BB | HR/9 | K% | BB% | WHIP | BABIP | RA | H/9 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 |  | M. Miller | 15.23 | 205.2 | 185 | 8 | 6 | .571 | 0 | 2.32 | 348 | 0 | 0 | 88 | 108 | 53 | 63 | 15 | 80 | 5 | 138 | 6 | 793 | 12 | 3.50 | 4.35 | 0.66 | 43.9 | 10.1 | 0.91 | .270 | 2.76 | 4.73 |
| 2 |  | E. DÃaz | 14.50 | 538.0 | 541 | 30 | 38 | .441 | 0 | 3.03 | 867 | 0 | 0 | 260 | 382 | 181 | 194 | 57 | 193 | 43 | 409 | 11 | 2,201 | 34 | 3.23 | 4.49 | 0.95 | 39.4 | 8.8 | 1.07 | .312 | 3.25 | 6.39 |
| 3 |  | D. Betances | 14.47 | 392.1 | 373 | 21 | 23 | .477 | 0 | 2.55 | 631 | 0 | 0 | 36 | 239 | 111 | 124 | 26 | 181 | 28 | 86 | 5 | 1,604 | 28 | 4.15 | 3.49 | 0.60 | 39.3 | 11.3 | 1.07 | .289 | 2.84 | 5.48 |
| 4 |  | A. Chapman | 14.45 | 873.0 | 916 | 63 | 51 | .553 | 0 | 2.48 | 1,402 | 0 | 0 | 402 | 510 | 241 | 268 | 57 | 431 | 34 | 607 | 7 | 3,554 | 90 | 4.44 | 3.25 | 0.59 | 39.4 | 12.1 | 1.08 | .278 | 2.76 | 5.26 |
| 5 |  | J. Hader | 14.28 | 557.0 | 513 | 38 | 33 | .535 | 0 | 2.50 | 884 | 0 | 0 | 252 | 301 | 155 | 170 | 66 | 213 | 24 | 358 | 6 | 2,186 | 20 | 3.44 | 4.15 | 1.07 | 40.4 | 9.7 | 0.92 | .235 | 2.75 | 4.86 |
| 6 | | D. Williams | 13.75 | 338.1 | 352 | 34 | 18 | .654 | 0 | 2.69 | 517 | 0 | 0 | 102 | 217 | 101 | 125 | 23 | 158 | 15 | 156 | 5 | 1,395 | 18 | 4.20 | 3.27 | 0.61 | 37.1 | 11.3 | 1.11 | .284 | 3.33 | 5.77 |
| 7 |  | C. Kimbrel | 13.71 | 867.2 | 897 | 57 | 53 | .518 | 0 | 2.69 | 1,322 | 0 | 0 | 441 | 532 | 259 | 290 | 79 | 368 | 43 | 674 | 13 | 3,502 | 74 | 3.82 | 3.59 | 0.82 | 37.7 | 10.5 | 1.04 | .268 | 3.01 | 5.52 |
| 8 | | F. Cruz | 12.95 | 237.2 | 244 | 11 | 20 | .355 | 0 | 4.09 | 342 | 0 | 0 | 4 | 183 | 108 | 117 | 26 | 126 | 8 | 35 | 4 | 1,018 | 23 | 4.77 | 2.71 | 0.98 | 33.6 | 12.4 | 1.30 | .304 | 4.43 | 6.93 |
| 9 | | A. Miller | 12.93 | 504.0 | 546 | 35 | 28 | .556 | 0 | 2.95 | 724 | 0 | 0 | 63 | 351 | 165 | 183 | 47 | 201 | 46 | 147 | 9 | 2,091 | 25 | 3.59 | 3.60 | 0.84 | 34.6 | 9.6 | 1.10 | .283 | 3.27 | 6.27 |
| 10 |  | C. Smith | 12.67 | 223.0 | 219 | 20 | 7 | .741 | 0 | 2.26 | 314 | 0 | 0 | 58 | 154 | 56 | 67 | 10 | 59 | 11 | 92 | 4 | 884 | 9 | 2.38 | 5.32 | 0.40 | 35.5 | 6.7 | 0.96 | .294 | 2.70 | 6.22 |
| 11 |  | A. Muñoz | 12.59 | 316.2 | 324 | 17 | 29 | .370 | 0 | 2.76 | 443 | 0 | 0 | 106 | 212 | 97 | 113 | 26 | 128 | 17 | 172 | 12 | 1,286 | 21 | 3.64 | 3.46 | 0.74 | 34.4 | 10.0 | 1.07 | .277 | 3.21 | 6.03 |
| 12 | | C. Marmol | 12.33 | 509.1 | 506 | 18 | 29 | .383 | 0 | 3.25 | 698 | 0 | 0 | 117 | 324 | 184 | 195 | 37 | 340 | 47 | 259 | 20 | 2,207 | 32 | 6.01 | 2.05 | 0.65 | 31.6 | 15.4 | 1.30 | .265 | 3.45 | 5.73 |
| 13 |  | K. Jansen | 12.30 | 972.1 | 984 | 58 | 46 | .558 | 0 | 2.60 | 1,329 | 0 | 0 | 497 | 634 | 281 | 302 | 95 | 305 | 33 | 739 | 21 | 3,860 | 22 | 2.82 | 4.36 | 0.88 | 34.4 | 7.9 | 0.97 | .257 | 2.80 | 5.87 |
| 14 | | K. Giles | 12.26 | 355.1 | 362 | 14 | 18 | .438 | 0 | 2.71 | 484 | 0 | 0 | 115 | 283 | 107 | 121 | 28 | 114 | 5 | 208 | 5 | 1,454 | 24 | 2.89 | 4.25 | 0.71 | 33.3 | 7.8 | 1.12 | .310 | 3.06 | 7.17 |
| 15 | | K. Yates | 12.24 | 493.1 | 517 | 32 | 29 | .525 | 0 | 3.36 | 671 | 0 | 0 | 101 | 364 | 184 | 199 | 66 | 198 | 33 | 232 | 13 | 2,055 | 19 | 3.61 | 3.39 | 1.20 | 32.7 | 9.6 | 1.14 | .274 | 3.63 | 6.64 |
| 16 | | R. Dibble | 12.17 | 477.0 | 385 | 27 | 25 | .519 | 0 | 2.98 | 645 | 0 | 0 | 89 | 332 | 158 | 169 | 27 | 238 | 12 | 204 | 25 | 1,979 | 36 | 4.49 | 2.71 | 0.51 | 32.6 | 12.0 | 1.19 | .289 | 3.19 | 6.26 |
| 17 | | T. Rosenthal | 12.12 | 364.0 | 373 | 12 | 25 | .324 | 0 | 3.36 | 490 | 0 | 0 | 132 | 304 | 136 | 145 | 19 | 177 | 22 | 207 | 8 | 1,570 | 23 | 4.38 | 2.77 | 0.47 | 31.2 | 11.3 | 1.32 | .331 | 3.59 | 7.52 |
| 18 | | B. Abreu | 12.11 | 392.1 | 383 | 22 | 16 | .579 | 0 | 2.82 | 528 | 0 | 0 | 25 | 283 | 123 | 135 | 34 | 189 | 27 | 90 | 0 | 1,637 | 27 | 4.34 | 2.79 | 0.78 | 32.3 | 11.5 | 1.20 | .290 | 3.10 | 6.49 |
| 19 | | C. Knebel | 12.05 | 301.0 | 308 | 13 | 16 | .448 | 0 | 3.29 | 403 | 0 | 0 | 72 | 231 | 110 | 121 | 34 | 143 | 11 | 137 | 13 | 1,260 | 7 | 4.28 | 2.82 | 1.02 | 32.0 | 11.3 | 1.24 | .294 | 3.62 | 6.91 |
| 20 | | A. Vesia | 11.98 | 331.1 | 371 | 20 | 14 | .588 | 0 | 2.88 | 441 | 0 | 0 | 16 | 212 | 106 | 126 | 38 | 157 | 12 | 53 | 16 | 1,365 | 9 | 4.26 | 2.81 | 1.03 | 32.3 | 11.5 | 1.11 | .243 | 3.42 | 5.76 |
| 21 | | B. Wagner | 11.92 | 903.0 | 853 | 47 | 40 | .540 | 0 | 2.31 | 1,196 | 0 | 0 | 422 | 601 | 232 | 262 | 82 | 300 | 33 | 703 | 26 | 3,600 | 43 | 2.99 | 3.99 | 0.82 | 33.2 | 8.3 | 1.00 | .261 | 2.61 | 5.99 |
| 22 | | B. Lidge | 11.92 | 600.1 | 602 | 26 | 32 | .448 | 0 | 3.55 | 795 | 0 | 0 | 225 | 490 | 237 | 257 | 57 | 285 | 33 | 368 | 41 | 2,576 | 46 | 4.27 | 2.79 | 0.85 | 30.9 | 11.1 | 1.29 | .308 | 3.85 | 7.35 |
| 23 | | D. Robertson | 11.84 | 893.1 | 880 | 68 | 46 | .596 | 0 | 2.93 | 1,175 | 0 | 0 | 179 | 674 | 291 | 315 | 81 | 364 | 25 | 358 | 38 | 3,687 | 57 | 3.67 | 3.23 | 0.82 | 31.9 | 9.9 | 1.16 | .290 | 3.17 | 6.79 |
| 24 | | M. Feliz | 11.82 | 249.2 | 227 | 17 | 8 | .680 | 0 | 5.12 | 328 | 0 | 0 | 1 | 237 | 142 | 151 | 42 | 108 | 7 | 54 | 2 | 1,091 | 18 | 3.89 | 3.04 | 1.51 | 30.1 | 9.9 | 1.38 | .322 | 5.44 | 8.54 |
| 25 | | J. Leclerc | 11.74 | 365.2 | 357 | 12 | 21 | .364 | 0 | 3.35 | 477 | 0 | 0 | 41 | 247 | 136 | 150 | 32 | 203 | 21 | 141 | 8 | 1,546 | 25 | 5.00 | 2.35 | 0.79 | 30.9 | 13.1 | 1.23 | .264 | 3.69 | 6.08 |
StatMuse has game-level data for K/9 and innings pitched going back to the 1901 season.
Some of the information used here was obtained free of charge from Retrosheet.
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| NL East | W | L | PCT | GB |
|---|---|---|---|---|
 Braves - y | 94 | 68 | .580 | |
 Phillies - w | 88 | 74 | .543 | 6.0 |
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| NL Central | W | L | PCT | GB |
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 Cubs - w | 89 | 73 | .549 | 14.0 |
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| NL West | W | L | PCT | GB |
 Dodgers - y | 100 | 62 | .617 | |
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|---|---|---|---|---|
 Rays - y | 98 | 64 | .605 | |
 Yankees - w | 93 | 68 | .578 | 4.5 |
 Red Sox - w | 87 | 75 | .537 | 11.0 |
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| AL Central | W | L | PCT | GB |
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 White Sox - w | 84 | 78 | .519 | 1.0 |
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69 | 93 | .426 | 16.0 | |
| AL West | W | L | PCT | GB |
 Astros - y | 81 | 81 | .500 | |
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62 | 100 | .383 | 19.0 |
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