According to then manager Gary Peters, he revealed that Mayor joined Preston North End at age nine for £40 after his parents enrolled him to do the club's Centre of Excellence and was given "free bottle of milk and a season ticket for coming to the school". He went on to come through Preston North End's youth ranks. On 15 December 2008 he was given his first professional two-and-a-half-year contract with fellow youngster, Adam Barton.
On 5 March 2009 he joined Tranmere Rovers on a one-month loan deal. Tranmere manager Ronnie Moore was reported to say: "He is a hard working winger with the ability to go past people and has a trick up his sleeve." Two days later, on 7 March 2009, He was handed his League One début against Northampton Town, where he set up a goal for Bas Savage. After the match, Manager Moore praised Mayor performance, citing he "direct, took people on and played a great ball in for the goal." After making three appearance, Mayor returned to Preston, where Manager Alan Irvine believes that the loan move to Tranmere Rovers made him "grow up", due to giving him "more confidence".
Mayor made his debut for Preston North End on 16 January 2010 against Bristol City. He came on as a substitute in the 70th minute for Richard Chaplow. Preston lost the match 4–2. It was Darren Ferguson's debut as Preston manager. Due to Ferguson started to use youngsters in the first team, He was handed his full home debut in a game against Scunthorpe United on 10 April 2010, a game which Preston won 3–2. At the start of 2010–11 season, Mayor signed a two-year contract that will keep him until 2013.
After making 21 league appearance in the 2010–11 season, which resulted the relegation to League One, Mayor scored his first League goal for Preston against his old club Tranmere Rovers on 26 September 2011. His next goal came against Hartlepool United, which went on to win the goal of the season for the club's 2011–12 season and also went on to be awarded the Young Player of the Year. The 2011–12 season proved to be a breakthrough for Mayor, as he made a very impressive displays and become the fan favourite.
Mayor allegedly told manager Graham Westley before the 2012/13 season that he would like to play at a higher level, with fellow team-mate Jamie Proctor making the same statement, despite the pair both being contracted to the club and part of the manager's plans. As a result of wanting to leave, Preston chairman Peter Ridsdale was unsure towards the Mayor and Proctor.
After his loan spell with Tranmere Rovers came to an end, Mayor's impressive performance at the club attracted interests from Premier League duo Bolton Wanderers and Blackburn Rovers.
After being unsettled at the club, Mayor was linked with a move to Blackpool, before a bid for Mayor from Championship side Sheffield Wednesday was accepted, with Manager Dave Jones stating that he "would be a good addition". One day later, Mayor joined the club for an undisclosed fee on a three-year contract.
Mayor made his debut on 1 September 2012 for the club, coming on as a substitute in the 84th minutes, in a 2–1 loss against Crystal Palace. He soon have his first team opportunities become limited since joining the club.
He joined Southend United on an initial 28-day loan deal on Tuesday 12 February 2013, going straight into the first team to play against Cheltenham Town that night. The move occurred when the club need a replacement for Michael Timlin, who ruled out for the entire of the season. After making five appearance, Mayor loan spell with Southend United came to an end.
Ahead of the 2013–14 season, Mayor joined Bury on a season-long loan, which will keep him until the end of the 2013–14 season. He made his debut, coming on as a substitute, in a 2–0 loss against Chesterfield in the opening game of the season. Four weeks later, on 31 August 2013, Mayor scored his first goal from a 30-yard strike, in a 4–1 win over Cheltenham Town before setting up the fourth goal. Since scoring his first goal, Mayor began established himself in the first team regular. Though becoming in the first team regular, Mayor struggled to score furthermore goals until scoring his second goal of the season, in a 3–0 win over Hartlepool United on 1 January 2014. He went on to make 42 appearance in all competitions and scoring five times.
At the end of the next season, Bury named Mayor as the Players' Player of the Season as part of End of Season Awards Dinner at the Village Hotel. It was also confirmed a Undisclosed Fee had been agreed with Sheffield Wednesday for his services, Mayor signed a three-year deal with Bury after the move was announced by the club's chairman, Stewart Day, who surprised fan at the End of Season Awards Dinner. Upon the move, Manager David Flitcroft believes Mayor has the experience of playing in "with Championship quality".
Mayor's first game after signing for the club on a permanent basis came in the opening game of the season, in a 1–0 loss against Cheltenham Town. Mayor's first goal after signing for the club on a permanent basis came three weeks later, in a 2–1 win over Accrington Stanley. Mayor later scored two goals in two games to add his second and third goal between 11 October 2014 and 18 October 2014 against Wimbledon and Portsmouth Mayor did the same thing again when he scored later scored two goals in two games to add his fifth and sixth goal between 26 December 2014 and 28 December 2014 against Northampton Town and Mansfield Town. Mayor finished the season with eight league goals (eight overall), which he was awarded as League Two Player of the Year and was also included in League Two's PFA Team of the Year.As of 2 September 2017
League Two Player of the Year: 2014–15