In the last 16 of the championships, Cahill commented he "couldn't believe how badly [he] had played" after his tournament ended with a 2–6 loss to Mark Davis. Cahill would have a poor end to the season as he lost seven out of eight matches after this which would have relegated him from the tour as he finished 85th in the world rankings. However, his performance in the European Tour events saw him finish high enough on the European Order of Merit to retain his spot on the tour for the following two seasons. In the 2015–16 season, Cahill failed to win more than one match at an event, winning just five matches all year. He competed at the main stage of the 2015 UK Championship, where he lost to Anthony McGill 6–3. Appearing at the 2016 Welsh Open, he won his first round match for the first time, defeating Xiao Guodong 4–1, but then lost 1–4 to Mark Davis. Cahill finished the season 110th in the rankings.