McDuffie was successful as an outfielder early in his career, hitting .297 and leading the league with 18 stolen bases with the Birmingham Black Barons in 1930. He became a strong pitcher with good control; with the Newark Eagles in 1938, he completed all 27 of the games he started. He was 27-5 in 1941, leading the Homestead Grays to the pennant. He was also the winning pitcher in his first East-West all-star game in ’41.
In 1945 McDuffie and Dave “Showboat” Thomas had tryouts with the Brooklyn Dodgers, largely as a publicity stunt forced on Branch Rickey by Joe Bostic, sports editor of the black newspaper People’s Voice. Both players were in their late thirties, past their prime. Rickey signed Jackie Robinson later that year.