P · 4 seasons · 1988 – 1991 · B/T: R/R
John Costello is the extreme version of a specialist. +1.3 of roto value came from ERA, yet his career total is only -2.9. The peak came in 1989, +0.9, 138th that season and 14933rd of 51,303 player-seasons on record. The value came from ERA (+1.3) and WHIP (+0.2). It leaked back out through strikeouts (-2.1) and saves (-0.8).
| Season ↑ | Tm | G | Z | Szn | All-Time |
|---|---|---|---|---|---|
| 1988 | STL | 36 | -2.37 | #854 | #93,581 |
| 1989 | STL | 48 | -2.44 | #889 | #97,137 |
| 1990 | STL | 8 | -2.19 | #504 | #76,022 |
| 1991★ | SD | 27 | -2.18 | #793 | #74,732 |
★ Best season by Z
| Season ↑ | Tm | G | Z | Szn | All-Time |
|---|---|---|---|---|---|
| 1988 | STL | 36 | 0.30 | #153 | #17,152 |
| 1989★ | STL | 48 | 0.92 | #138 | #14,933 |
| 1990 | MON | 8 | -2.44 | #357 | #38,285 |
| 1991 | SD | 27 | -1.72 | #266 | #28,430 |
★ Best season by Z