A man who never played professionally, who spent years coaching at non-league clubs and south London charities, and who only joined Chelsea's first-team setup in January, is now the man tasked with taking the club to Wembley for an FA Cup semi-final against Leeds United on Sunday.
It is his second spell as Chelsea's interim head coach this season. The first lasted two games. This one could stretch to six if they reach the final.
McFarlane grew up in Forest Hill, south London, and by his own description was a "failed footballer." He moved into youth coaching, taking part-time roles at Crystal Palace and Fulham's academies while simultaneously helping run Lambeth Tigers, a grassroots club in south London.
It was there, in 2012, that a chance encounter changed his life. Two Norwegian boys training at the club happened to be the sons of Thomas Hafstad, a former Tromsø player. Hafstad, who now serves as the club's technical director, spotted something in McFarlane immediately.
"Instantly, I could see Calum was a very good coach," Hafstad told BBC Sport. "He listened to the players — young boys of 11 and 12 — and really understood how to work with them. What stood out most was his man-management."
Hafstad took McFarlane to Tromsø — the northernmost professional football club in the world — initially to run the Under-14 side. He progressed to the Under-19s, took first-team sessions, and worked at a club competing in European football.
He returned to London in 2014, joining the Kinetic Foundation, a south London charity that supports disadvantaged young people through football and education. He stayed for six years, earning a reputation for getting boys into professional academies. The charity has since produced three members of Chelsea's current coaching staff — McFarlane, his assistant Harry Hudson, and Dan Hogan. That connection has attracted abuse on social media from some Chelsea supporters frustrated by the club's recent results, something the charity's co-founder James Fotheringham described as "regrettable."
Stints at Manchester City's academy and Southampton — where he rose to head coach of the Under-21s — followed before Chelsea recruited him in July 2025 to run their own Under-21 operation.
He holds a UEFA A licence but not a Pro licence, meaning he can only serve as caretaker for a maximum of 12 weeks. He would need to be enrolled in the Pro licence course to be considered for a permanent appointment.
His first spell in interim charge came on New Year's Day, when a call from the sporting directors diverted him from a planned family trip to a light show to take training ahead of a fixture at Manchester City. His side drew 1-1. He was described by Chelsea officials as having shown "professionalism and composure" in a demanding situation.
Rosenior then kept him on as first-team coach. When Rosenior was sacked on Wednesday, McFarlane was promoted again.
"It's a whirlwind, but what happens, happens," he said. "I know it's been tough recently but there's a lot of talent. Some of those players in there are some of the best players in the world for their position. There's still a belief within us. We can turn this around and get our season back on track."
Chelsea play Leeds at Wembley on Sunday. McFarlane has never previously visited the stadium as anything other than a spectator.