Centre-back Gavin Gunning joined Blues during the summer of 2014 after leaving Dundee United.
The Dubliner was recruited on a one-year deal, with a further 12 month option.
The former Republic of Ireland U21 international, had spent the last three seasons at Dundee United, where he racked up 99 appearances scoring ten goals in the process.
Prior to arriving at Tannadice Park in August 2011, the Irishman was a Blackburn Rovers trainee who enjoyed loan spells with Tranmere Rovers, Rotherham United, Bury and Motherwell, before moving north of the border.
Unluckily for Gunning he suffered posterior cruciate ligament damage on his debut for Blues against Cambridge United in the Capital One Cup in August 2014.
The player underwent surgery which kept out until March 2015.