Duffy qualified for the 2011/2012 professional Main Tour as one of four semi-finalists from the third and final Q School event.
Duffy had a poor 2012/2013 season as he lost his first six games and only won a total of four matches in ranking event qualifiers and two matches in Players Tour Championship tournaments. He finished a lowly 108th on the PTC Order of Merit, but did end the season ranked world number 60, his highest ranking to date.
He played in the final qualifying round for the Shanghai Masters after winning three matches, but was edged out 5–4 by Robert Milkins. Duffy lost in the second round of both the Paul Hunter Classic and Northern Ireland Open 4–1 to Lee Walker and 4–3 to Peter Ebdon respectively. He was beaten in eight of his final nine matches of the season after this.
In the first round of the 2015 UK Championship, Duffy pulled off a huge shock by eliminating world number nine and two-time winner of the event Ding Junhui 6–2. He credited the win to working hard on his game at the academy in Sheffield. He forced a deciding frame against Joe Swail in the next round having been 5–3 down, but lost it. He qualified for the China Open by beating Thepchaiya Un-Nooh 5–3, but would later withdraw from the event. Duffy lost in the final round of the EBSA Qualifying Tour Play-Offs to Sam Craigie, but by twice losing in the fifth round of Q School he earned a two-year tour card via the Order of Merit.