An overpowering right-handed pitcher, Mark played for the St. Louis Union Printers from 1980-92, helping them win two national championships. In 1984, he was the player/manager of the Printers, who won the national title that year and the next. Hahn led his team to five league championships.

In 1996, Hahn was elected to the Union Printers International Baseball League Hall of Fame. He has been the head baseball coach at Pattonville High School since 1997, winning nine conference championships. Hahn also served as coach of the St. Louis Grizzlies.