Thurstans was drafted from the Dandenong Stingrays at selection 39 in the 1998 National AFL Draft. He could not get a game and played in the South Australian National Football League (SANFL) for Sturt until his AFL debut for Port Adelaide in Round 1, 2003 versus West Coast Eagles at Subiaco. Thurstans won Port's best first year player award for season 2003. The following season he played all 25 games, kicked 28 goals, played in the 2004 AFL Grand Final and was one of three players to kick three or more goals in Port's 40 point Grand Final win over the Brisbane Lions.