Colin has struggled through the last three seasons with hardly any first team games. He played a few at the start of the title season before picking up an injury, and the same thing happened in the SPL seasons. Last season he only played a few under 21 games towards the end.
A recurring pelvic injury, combined with a back injury, are what have forced Colin to retire at such a young age. The pelvic injury is similar to what forced Barry Lavet to quit Saints and tour various nothing clubs, with the exception of Clydebank. He's been with the club 5 years and hasn't played many games due to his injury.
Mirren Mad wants to wish Colin all the best in whatever he does in the future.