Sandy Koufax. He wasn't terrible. In a 6-year run starting in 1961 Koufax was won 129 games, losing only 47, leading the league in ERA 5 times, FIP every year, shutouts three times and strikeouts on 4 occasions. He also had the best WHIP in four years, H/9 innings and K/9 innings five times and in strikeout/walk ratio three times.
Sandy Koufax ~ "Sanford 'Sandy' Koufax (December 30, 1935) is an American former left-handed baseball pitcher who played his entire 12-year Major League Baseball (MLB) career for the Brooklyn/Los Angeles Dodgers (1955–1966). Retiring at the peak of his career, in 1972 he became, at age 36 and 20 days, the youngest player ever elected to the Baseball Hall of Fame. Koufax's career peaked with a run of six outstanding seasons from 1961 to 1966, before arthritis in his left elbow ended his…"