Duffy made his first-grade debut for Parramatta against the Canberra Raiders in Round 2 1983 at Belmore Oval. Parramatta would go on to reach the 1983 NSWRL grand final in a rematch against Manly from the previous season. Duffy was selected by coach Jack Gibson to play from the bench. Parramatta went on to win the match 18-6 and claim their third straight premiership. As of the 2019 NRL season, no other club has won 3 premierships in a row since.
