Coleman overcame a 9-32 minor league record to twice win 20 games in the big leagues. The first player chosen by the Senators in the initial 1965 free agent draft, he had his best years after going to Detroit in an eight-player deal for Denny McLain in 1970. He won 20 games in 1971, 19 in 1972, and a career-high 23 in 1973. In Game Three of the 1972 LCS, he shut out Oakland 3-0, striking out an LCS-record 14 batters. After going 10-18 (5.55) in 1975, Coleman worked for six teams in four years, mostly out of the bullpen.
The son of Joseph Patrick Coleman, the two rank third in father-son combined wins, their 194 victories placing them behind the Bagbys and the Trouts.