Gedeon signed with the Washington Senators after graduating in the summer of 1939. He chose to sign with the Senators over a possible appearance as a member of the USA's track team in the 1940 Summer Olympics. Gedeon was quite a prospect; Clark Griffith, president of the Senators, mentioned Gedeon to "The Sporting News" on June 15, when talking about exciting new players: "We've got ... a youngster from the University of Michigan named Gedeon." Gedeon was initially assigned to a minor league baseball team in Orlando, Florida where he played in 67 games in 1939. In mid-September, he was called up to the major leagues where he appeared in five games as an outfielder with three hits, one run and one RBI. His three hits came in a 10–9 win against the Cleveland Indians on September 19 as the starting centerfielder. In his five major league games, he played four games in center field and one in right field.