2012 League Cup final. Harris was only called into the first team squad on one occasion during the 2012–13 Championship-winning season, when he made his debut in a 2–1 FA Cup third round defeat against Macclesfield Town on 5 January 2013. Harris started the match and was substituted for Tommy O'Sullivan after 64 minutes. Harris received his first call into the first team squad of the 2013–14 season on 28 August 2013, when he was an unused substitute for a 2–0 League Cup first round win over Accrington Stanley. He was again an unused substitute in the following round, which saw Cardiff lose 3–2 to fellow Premier League side West Ham United. Loans Spells After putting in an "outstanding" performance for Cardiff in a Professional Development League game versus Brentford, on 18 October 2013 Harris joined the League One side on a loan running until 5 January 2014. The following day, he was included in the squad to face Colchester United and after replacing Will Grigg on 65 minutes, he scored the first senior goal of his career in a 3–1 win. Harris scored his second Brentford goal in an FA Cup first round tie against local neighbours Staines Town on 9 November, scoring the second in a 5–0 victory. Harris was stretchered off with a hamstring problem in a 3–0 victory over Preston North End on 21 December, casting doubt on his loan being extended. On 26 December it was reported that Harris would be out for a month, with manager Mark Warburton keen on extending the loan. Harris tweeted on 29 December that he would be returning to Cardiff, leaving plans to extend his loan up in the air. Harris made 11 appearances for Brentford and scored two goals. It was reported in mid-March 2014 that Harris was close to a return to the Bees to cover for the injured Sam Saunders, despite being sidelined with an ankle injury himself. The following season, Harris started to become a regular under new manager, Russell Slade, who was appointed in October. He played his first league game for Cardiff in a 5–3 loss to Bournemouth, on 20 December. Harris scored his first goal for The Bluebirds in a FA Cup win against Colchester United, following this with his first league goal against Norwich City. On 22 August 2015, Harris joined League One side Barnsley on loan until 21 November 2015.