Colquhoun was South Australia's Most Valuable Player and an All-Australian at the 2012 AFL Under 18 Championships.
He had a solid Finals series in 2013, providing trustworthy disposals off half back against Collingwood and Geelong.
He struggled for game time in the pre-season and was left out of the round one team.
He then played a handful of games for the Magpies before injuring his knee and requiring a full reconstruction ending his season.
His best games came against Sydney and Carlton, before heading back to the SANFL for the finals.