Kayal made his debut for Celtic against FC Utrecht on 19 August 2010 and showed his full potential by getting off to the best possible start, setting up the opening goal of the game for Efraín Juárez and winning the Man of the Match award. In September 2010 he suffered a setback and was out of action for three months due to a hernia injury which required surgery. He made his return as a substitute on 26 December against St Johnstone, and was restored to the starting line-up in a 2–0 win over Rangers at Ibrox on 2 January 2011.