his placed header struck the foot of the post. In the return, Caldwell helped the club beat Nacional 3–0 advance to the Group Stage. Since making his debut for Birmingham City, he quickly became a first team regular, forming a centre–back partnership with Curtis Davies. Caldwell then helped the club keep four consecutive clean sheets between 16 October 2011 and 29 October 2011. His performance was praised by Manager Chris Hughton for his dedication and commitment to the team. In return, he praised his philosophy, comparing it to his former manager Owen Coyle and even going far as to say "the best sort of manager to play for". Caldwell also captained Birmingham City's matches in the UEFA Europa League group stage, as they were eliminated. He successfully predicted that if the club failed to qualify for the Europa League knockout stage, it would be a disappointment. Once again, Caldwell helped the club keep four consecutive clean sheets between 14 January 2012 and 28 January 2012. In the absent of Stephen Carr and Liam Ridgewell, he captained Birmingham City for the rest of the 2011–12 season. Caldwell stated on two occasions that the club can win the promotion back to the Premier League. However in a match against Ipswich Town on 17 April 2012, he suffered a groin injury and was substituted in the 35th minute, as Birmingham City drew 1–1. After the match, it was announced that Caldwell was sidelined for the rest of the 2011–12 season. He previously missed a match against Watford on 28 August 2011. Caldwell's groin injury was considered to be a loss among the club's supporters, considering his contribution he has done this season so far. However in his absent, Birmingham City lost 3–2 against Blackpool in the semi–finals of the Championship play–offs. At the end of the 2011–12 season, Caldwell went on to make fifty–two appearances in all competitions. Ahead of the 2012–13 season, Caldwell made his return from injury for Birmingham City and featured in a first half friendly match against Borussia Mönchengladbach on 21 July 2012, as the club drew 2–2. He continued to go to the rehabilitation to recover from his groin injury, with Manager Lee Clark saying the situation is monitoring carefully. At the start of the 2012–13 season, Caldwell scored his first goal for Birmingham City on 14 August 2012 in a 5–1 win over Barnet in the League