Born in Hertford, Bentley started his playing career with Aveley before moving on to Enfield in August 1998. He later moved to Aldershot Town, Gravesend & Northfleet (where he won Player of the Year in 2002–03) and Dagenham & Redbridge. On 15 January 2004, he stepped up into The Football League when he signed for Southend United, where he made 93 league appearances including 23 as a sub. He also scored 12 league goals including five in his last season at Roots Hall and was involved in two consecutive promotions. He was offered a new one-year contract to stay at Southend, but opted to go for the security of a two-year deal at Gillingham, signing for them on 22 May 2006. He made his debut in the 2–1 home win over Huddersfield Town on 5 August and scored his first goal away to Bradford City in a 4–2 defeat on 12 August.
