Competing as an amateur, Cahill appearing in two professional events, at the 2017 Snooker Shoot-Out, where he defeated Rory McLeod before losing to Graeme Dott, and the 2018 Gibraltar Open where he defeated Eden Sharav 4–1, before losing to Noppon Saengkham 1–4. Post-season, Cahill entered Q-School once again. He reached the fifth round of all three events. At the first event he lost to Jordan Brown 4–1, the second event, to Jamie Cope, and Kuldesh Johal 3–4 in the final event Having only reached the fifth round, he did not win a place back on tour for the next season, and returned to being an amateur player.