Callum is an adept winger who prefers to play in central midfield. He has been with Manchester United since the age of 8 when he was coveted by Leeds United, Sheffield Wednesday and Sheffield United whilst at Barnsley. He made his Under-18 debut as a substitute away to Blackburn Rovers in October 2014 whist still an Under-16. His first start came in the final game of the 2014/15 season.
Callum became a regular in the Under-18 side during the 2015/16 and scored his first goal for the club in the FA Youth Cup tie against Queens Park Rangers in December 2015. Callum made his Under-21 debut in February 2016 away to Blackpool.
Callum joined Port Vale on loan in January 2019 before being released by Manchester United at the end of the 2018/19 season.