An excellent running back from both the single wing and T-formations, Kretz won letters on the football teams of 1942, 1946 and 1947. He captained 1947 team. Kretz was named to United Press All-Eastern team and received Associated Press All-America honorable mention in 1942. He also received Newspaper Enterprise Association All-America honorable mention in 1946, in addition to earning AP All-East honorable mention. He led the 1946 team in rushing on 88 carries for 594 yards and a school-best net rushing average per carry of 6.8. He was second on the team in scoring (30 points) in 1946. After college, he signed to play with the Brooklyn Dodgers of the All-American Football Conference.
