In one season with Decatur in the Three-I League, Schupp pitched 356 innings in 51 games. He reputedly had so much “stuff” that some teammates were afraid to catch him. He became the regular closer for rebuilding Giants teams. In his one season as a full-time starter for the Giants, he was 21-7 for the 1917 NL champions, leading the league in winning percentage. He was knocked out in the second inning of Game Two of the World Series, but came back to shut out the White Sox in Game Four. Schupp lost his effectiveness after serving in WWI.