The local lad began his career across the water with Tranmere Rovers where he would only make 11 appearances before moving to soon-to-be promoted Sunderland in 2002.
Sean made his debut for the Wearsiders against Bolton Wanderers in the third round of the FA Cup in january 2003 but was unable to stop Sunderland’s relegation to the First Division.
He was sold to Doncaster Rovers in 2005 where he would spend two injury filled seasons before being released. Thornton was quickly captured by Leyton Orient where he scored a long range free kick on his debut.
In 2011, Thornton moved to Wales where he had spells with Aberystwyth Town, Conwy Borough and Bala Town before returning home in 2015 to play for Drogheda. He impressed in a side that ultimately finished bottom as he scored five times in 28 games before re-signing for 2016.
Named captain by manager Pete Mahon, Sean made a fine start to the season before damaging ankle ligaments in a 2-2 draw with Athlone Town ruled him out for six weeks. He would make 28 appearances in all competitions, scoring eight times including the crucial winning goal against Wexford Youths in the play-offs.
Sean re-signed for a third year with Drogheda in November 2017.
Tranmere Rovers (2001-2002)
Blackpool (loan) (2002)
Doncaster Rovers (2005-2007)
Leyton Orient (2007-2010)
Shewsbury Town (loan) (2008)
Aberystwyth Town (2011-2013)
Conwy Borough (2013)
Bala Town (2014)
Drogheda United (2015-)
Football League Championship 2004-2005