Duffy has enjoyed a successful debut season in the Zurich Premiership, with Quins fans quick to recognise his strong running and safe hands under the high ball.
"I am trying to be more consistent in my play, especially with my kicking from hand and the timing of when to come into the line in attack," he said. "I feel I can up my performances a little bit before the end of the season."
Duffy chose to join Harlequins largely because of Will Greenwood and coach John Kingston.
"Will's mind is so sharp - he sees things so quickly and I've learned so much from him already," said Duffy.
"Knowing John from when he was coach at Galwegians has really helped me settle in, as has the presence here of other Irish players Mel Deane, Andy Dunne, Simon Keogh and Paul Burke."
