Cahill managed to win just three matches during the 2013/2014 season, and ended his debut season on tour ranked world number 117. Cahill played in the main stages in the 2013 UK Championship and the 2013 Welsh Open, but did not progress past the first round in either competition, losing to Joe Perry 6–3, and Ken Doherty 4–0 respectively. Cahill's second season saw him improve his results as he twice reached the last 32 in the minor-ranking European Tour events. At 18-years-old, he then went on his best run to date in a ranking event during the 2014 UK Championship. He won comfortably in the first round, beating veteran Mark King 6–0 and then saw off former Welsh Open finalist Andrew Higginson 6–4. Cahill faced world number three Ding Junhui, a player who had won five ranking titles the previous season, and raced into a 5–1 lead. Ding won three frames in a row and needed three snookers in the next frame, which he got when Cahill left a . Cahill responded by taking the deciding frame to record the biggest victory of his career up to that point.