Originally from Dampier, Western Australia, he debuted with East Perth in the West Australian Football League (WAFL) in 2000.

A ruckman, Cox was named in the All-Australian team six times, including four seasons consecutively from 2005 to 2008, and was considered the outstanding player in his position throughout much of his career.

His uncle George Michalczyk, a former Australian rules player himself, recommended Cox to the club he began his senior career with, East Perth.

Cox played colts for East Perth in 1999 and at the end of the season was invited to train with the West Coast Eagles in their pre-season.

Two incidents stand out in particular for Cox – one where in the Qualifying Final against Sydney he took two saving marks in defence to secure the game in the dying moments, where his team got home by less than a goal.

He continued his good form and established himself as one of the league's premier ruckmen, averaging over 20 hitouts and almost 20 disposals per game through Round 8 of the 2006 Season.

The departure of Ben Cousins and Chris Judd (Carlton) and questions surrounding the clubs culture meant that Cox had to step up.

Standout games included the Semi-Final against Collingwood in 2007 that went to extra time (which West Coast lost), where Cox collected 27 disposals, 9 marks, 29 hitouts and a goal.

[10] Cox married Kerry Lavell at a ceremony at Leeuwin Estate in Margaret River in December 2011, having dated her for three years previously.