Burnell started his career with Bristol City and he became an integral part of the midfield set-up at Ashton Gate. His stirring displays were enough to earn him a long-term contract and a short spell as the club's captain.
Burnell joined Wycombe Wanderers in July 2004 after Tony Adams' summer clearout which saw the departure of Michael Simpson, Dannie Bulman, Steve Brown and Darren Currie. Burnell was hoping to gain a regular first team place and after a season blighted by injury and illness he formed a midfield trio with Matt Bloomfield and Keith Ryan.
Burnell was also a regular under John Gorman and consequently followed his manager when he left Wycombe to join Northampton Town in July 2006. During his time at Northampton was constantly a good performer being named captain on occasions in the absence of Chris Doig and Mark Hughes.
On 21 April 2008, it was announced that he would be released at the end of the 2007/8 season, which was a surprise to most fans.
Burnell signed for Oxford on July 1, 2008, but in April 2009 it was announced that he no longer had a future at the club. After a successful trial at Exeter he joined them on 9 July 2009 on a free transfer.
It was announced on 14 May 2010 that he had been released by Exeter, along with 8 other players On 13 July 2010, Burnell joined Conference National side Bath City.