"Mackin played in the opening match of 2009–10, a 2–1 defeat away to Oxford on 8 August 2009, and according to "The Press" was a "strong presence in the City midfield in a very committed performance".A foot infection led to him missing a match against Gateshead on 25 August 2009 and he made his return in a 2–0 home win over Crawley Town on 5 September as an 84th-minute substitute.