Sean re-signed for Rugby Town in July 2017 after a successful trial.

Castleton progressed through the youth ranks at Rugby Town to make his debut in 2009.

A multiple Player of the Season winner for the youth team, the then 19-year-old defender made his debut for the first team in 2009 as a substitute against Banbury United.

Sean left the club at the end of the season after Martin Sockett's arrival and has since played locally including for AEI Rugby.

Castleton featured regularly under Dave Stringer during the 2017/18 MFL Premier campaign before leaving the club in June 2018.