Career
Before joining Adelaide United for the A-League 2007-2008 season, Mullen played for the Para Hills Knights in the South Australian Premier League and with the Australian Institute of Sport. He made two substitute appearances over his one-year contract with Adelaide and was signed as a youth player for the A-League 2008-2009 season. After some impressive performances in the A-League National Youth League Mullen was awarded a place on the bench against Wellington Phoenix.
He replaced Angelo Costanzo in the 67th minute playing his part in the 1–1 draw.
Since 2009 he has been loaned out to local Adelaide clubs Adelaide City and Para Hills Knights during the A-League off season.
