Mackey started his career at Coventry City where he made three appearances. The first on 12 April 2003 against Ipswich Town meant that he was the youngest player ever to take the pitch for the club's first team, aged 16 years and 167 days. At the start of the 2005–06 season Mackey had a trial with Linfield of the Irish Premier League. He made four appearances for them and scored one goal. At the start of the 2006–07 season Mackey joined Leamington where he has had the chance to get more first team experience. That season he was Leamington's highest scorer and repeated the feat in 2007–08. 2007–08 saw him become the first player to sign a contract with the club since they reformed in 2000. This showed both the club's high regard for Mackey and his loyalty to the club after rumours that Nuneaton Borough of the Conference North were interested in signing him. After 92 games and 57 goals Mackey moved to Brackley Town at the end of May 2008, signing a two-year contract with the Southern League Premier Division outfit. He then signed for Conference North sideCorby Town in June 2010 where he scored 10 league goals in the first half of the 2010/11 season before breaking his leg. In November 2011, Mackey signed for Evesham United, who at the time played in the Southern Football League. In 2011–12 he moved to St Neots Town and helped them win the Southern League Central Division title in 2011–12. The following season, he moved to Stourbridge and finished second highest scorer in the league with 29 goals. He then signed for Hemel Hempstead Town where he set the club record for number of goals scored in one season whilst helping them win the league title. On 13 May 2015, it was announced that Mackey was returning to Leamington, initially for pre-season training but with the aim to play for them during the 2015–16 Southern Football League season. He finished the season as the club's top goal scorer with 15 in the league and six in cup matches. Mackey started the 2016–17 season playing for Coventry United.
Mackey signed for Racing Club Warwick prior to the 2018–19 season. The striker adapted to his new surroundings quickly and had an excellent start the season scoring 5 goals in his first 3 three games before picking up a minor injury against Coleshill Town which would keep him out until September. He then went on to score 14 goals in his next 10 games before going on a 4-game goal drought he ended the drought against Paget Rangers on 26 December 2018, Mackey went on to score another 18 goals from then until the end of the season which included 6 braces and a hat trick, Mackey finished the seasons the clubs top goalscorer with 37 Goals in all competitions and was instrumental in the club finishing 2nd in the Midland Football League Division One securing automatic promotion to the premier division it was the clubs first promotion in over 30 years. Following a spell with Coventry United, Mackey returned to Racing Club Warwick on 31 January 2020.
