Lefty Grove, LHP
Career: 1925-41, A's, Red Sox
Fun fact: Faced Babe Ruth for 10 years, gave up only nine homers to him
Tough to imagine a better four-year stretch than what Grove had from 1928-31, when he went 103-23. That includes a 31-4 record with a 2.06 ERA and 27 complete games in 1931. Led AL in ERA nine times and led the league in strikeouts in each of his first seven seasons.
The man won 300 games (300-141) in 17 years, after he'd won 111 in the minors.