Walter Johnson is the youngest with 300+ strikeouts with an ERA better than 1.50 in a season. He was 22 years old in 1910.
| NAME | AGE | SO | ERA | SEASON | TM | G | W | L | W% | GS | 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 |  | W. Johnson | 22 | 313 | 1.36 | 1910 |  WSH | 45 | 25 | 17 | .595 | 42 | 38 | 8 | 1 | 370.0 | 262 | 56 | 92 | 1 | 76 | 13 | 3 | 1,367 | 21 | 7.61 | 1.85 | 4.12 | 0.02 | 22.9 | 5.6 | 0.91 | .271 | 2.24 | 56 | 1.39 | 56 | 6.37 | 45.2 | |
| 2 | | W. Johnson | 24 | 303 | 1.39 | 1912 | WSH | 50 | 33 | 12 | .733 | 37 | 34 | 7 | 2 | 369.0 | 259 | 57 | 89 | 2 | 76 | 16 | 13 | 1,413 | 11 | 7.39 | 1.85 | 3.99 | 0.05 | 21.4 | 5.4 | 0.91 | .253 | 2.17 | 42 | 2.03 | 63 | 6.32 | 49.6 | |
| 3 |  | O. Hoss Radbourn | 29 | 441 | 1.38 | 1884 | PRO | 75 | 59 | 12 | .831 | 73 | 73 | 11 | 2 | 678.2 | 528 | 104 | 216 | 18 | 98 | 2 | 2,672 | 34 | 5.85 | 1.30 | 4.50 | 0.24 | 16.5 | 3.7 | 0.92 | 2.86 | 48 | 2.75 | 84 | 7.00 | 31.9 |
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