Jason made his debut for the Norwich City first team on 5 April 2003 in a league match at Derby County. He started his first match in the Premiership on 28 February 2005 in a home game against Manchester City. Although Norwich lost 3-2, he acquitted himself well and kept his place in the centre of defence for the remaining 11 games of the season. Although the campaign would end with Norwich being relegated from the Premiership, Jason's ability, confidence and influence on his team-mates led many supporters to see him as a future Norwich captain. Season 2007-08 he is captain of the first team and has now made over 100 appearances. At the start of the 2008 season Jason signed for Wolves but could not maintain a regular place in the side and returned on loan to Norwich in February 2009. It was a unique end to the season for Jason because Norwich were relegated from the Championship but as he had played in 12 games for Wolves prior to his loan spell received a winners medal when they won the Championship and were promoted to the Premiership. Currently out of favour at Wolves Jason is spending the 2009-2010 season at Championship side Doncaster Rovers.