Dons Chorley made his first-team debut for Wimbledon immediately after signing for the club, playing the whole match in a 2–0 victory over Millwall at Selhurst Park on 15 March 2003. He went on to make ten appearances during the latter stages of the 2002–03 season. The following campaign was Chorley's breakthrough year in first-team football, playing regularly for Wimbledon in what was ultimately their last season before the club relocated to Milton Keynes. Chorley scored his first goal in professional football in April 2004, netting the only goal of the game as Wimbledon beat eventual champions Wigan Athletic at the JJB Stadium. A week after scoring his first ever goal, he doubled his goal tally, netting in a 3–3 home draw with Preston North End. Chorley was part of the starting line-up for Wimbledon's 1–0 victory over Derby County, the club's last ever league match as Wimbledon. He made 38 appearances during the campaign, a season in which Wimbledon were relegated to League One after finishing bottom of the league table. Chorley opted to play for the club under their new guise, Milton Keynes Dons, following the club's relocation from Wimbledon to Milton Keynes. He admitted the decision was difficult, due to Wimbledon being very local for him, whilst he had to travel "quite far" to Milton Keynes. Chorley was made club captain during the season. He made his first appearance of the 2004–05 campaign in a 3–1 home loss to Bournemouth on 21 August 2004. He scored two goals within the space of three days in October 2004; firstly scoring a header in a 3–2 defeat to Hull City, before netting a late consolation goal from the penalty spot as MK Dons were defeated 3–1 at Huddersfield Town. The two goals turned out to be Chorley's only goals of the season, as he went on to make 47 appearances for the club in all competitions. This included an appearance on the final day of the season; a 2–1 home win over Tranmere Rovers ultimately meant MK Dons survived relegation to League Two, with Torquay United suffering relegation instead on goal difference. A month after securing League One status for another season, in June 2005, Chorley signed a new two-year with the club. MK Dons manager Danny Wilson stated – "He is a tremendous captain and solid centre-half – you look for strong characters to lead the team and