Duffy made his professional debut with the Crushers on June 22, 2011, against the London Rippers. His 2012 season was cut short due to an arm injury. He went 1-0 with the Crushers in 2012, with a 3.37 ERA. He appeared in seven games, made one start, and won his first game in a relief role against Schaumburg, on July 17. He tossed two scoreless innings of relief to preserve a 3-2 victory. Duffy attended Mercyhurst University, where had two sensational seasons. His junior year (2011) spot starter for the Lakers, picking up a 4-1 record in 12 appearances, finished with a 1.88 ERA after allowing 11 runs, eight earned, on 23 hits in 38.1 innings of work, struck out 54 while walking 16. In 2012 he went 7-1 with a 3.34 ERA over 13 appearances, including 12 starts. Fanned 92 batters over 72.2 innings of action.