[2] Born in Irvine, raised in Troon and a product of the youth system at Kilmarnock,[3] McKenzie made his senior debut for the club as a substitute in a 1–1 draw against Inverness CT on 9 April 2011.

He then started his first game against Dundee Utd on 25 August 2012, where he scored a minute into the second half, as Killie went on to win 3–1.

[6] In the 2014–15 season, McKenzie scored the only goal in a 1–0 win over Ayr United in the Ayrshire Derby.

[7] He signed a further contract in summer 2016, and was the only one of several home-grown players to remain at the club after the squad was overhauled following an 11th-place finish in the Scottish Premiership which required them to defeat Falkirk to keep their place in the top division.

[11] He is also eligible to play for the Trinidad and Tobago national football team through a grandmother.