Born in Salford, Mainwaring, came through Preston North End's Centre of Excellence youth system before signing a 12-month contract with Stockport in June 2008.

[1] This was with the intention of being part of the development squad while trying to establish himself in Stockport's first team by the end of the season.

[2] He made his debut for the club on 30 August 2008, coming on as a substitute in a 0–3 defeat against Scunthorpe United.

[5] Mainwaring was injured in a friendly pre-season match against Grimsby Town on 25 July 2009, spelled a lengthy period out of the matchday squad, being out of action for 9 months with a broken leg, in January 2010 he told the Stockport Express "I've been out for five months and I'm desperate to get back.

[7] He went on trial with Hull City in November 2011 and subsequently signed a contract with the club in January 2012.

[1] Speaking after the programme in 2004, David Beckham said: "What I think impressed me about Matthew was when he was up against another of the hotshots Mollie, he was giving her a little bit of a chance, whereas some young kids wouldn't care.