Baseball people often characterized Foster as one of the game's great players. Umpire Jocko Conlan said Foster had "the same perfect delivery of Herb Pennock, but was faster by far, with a sharp curve, and had what all great pitchers have – control." Charlie Gehringer once told Foster, "If I could paint you white I could get $150,000 for you right now." Negro league player and manager Dave Malarcher favorably compared him to Negro league legend Satchel Paige, saying, "Bill Foster was my star pitcher, the greatest pitcher of our time, not even barring Satchel."