Matt Green joined Blues in July 2013 on a two-year contract.
Lee Clark moved quickly to sign the hottest property in non-league football following Green's impressive scoring record for Mansfield Town.
The ex-England schoolboy international hit 56 goals over the last two campaigns for the Stags, who were promoted to League Two last season having been crowned Blue Square Bet Premier champions.
Born in Bath, Green began his senior career at Newport County before signing for Cardiff City in 2007. With first-team opportunities limited and following loan spells at Darlington and Oxford United, the former Bristol City trainee moved to Torquay United a year later.
Having again linked up with Oxford on loan in 2009, Green scored the opening goal at Wembley in the Blue Square Bet Premier play-off final as The Us gained promotion to the Football League before the move was made permanent.
After finishing the 2010/11 season on-loan at Cheltenham Town, the one-time England C international went on to hit his red-hot scoring streak with Mansfield.
Having made just 12 appearances for Blues, Green suffered knee ligament damage during training in November 2013, which prematurely ended his season.