The 21-year-old, who has recently chosen to play for Scotland over England, was placed alongside Matic in a midfield pivot after Paul Pogba suffered an injury on the eve of the game.
And he produced a wonderfully dedicated performance, making a series of important interceptions and helping to stem the flow of Liverpool’s attack through the middle through his sheer energy.
Speaking soon after the game, Matic claimed that it was a joy to play alongside the midfielder.
“Scott is fantastic, it is a joy to play next to him,” he said. “He fights for the team, he runs a lot.”
“He plays like he’s already played five or six years in the Premier League but he’s still young. He was one of the best players on the pitch so I am happy that we have him in the team and he needs to continue in this way.”
For a man who apparently disdains the promotion of youth players, Mourinho deserves enormous credit for giving McTominay a start in one of the biggest games of United’s season just a few days on from a shocking display at Crystal Palace.
That level of faith galvanised McTominay, who stormed around the pitch for 90 minutes with an almost rapid sense of determination.
Anyone who came near his zone of the pitch was immediately closed down, consigned to following blind alleys and often kicked in one way or another. Never once did his energy levels or core strength ever seem to drop, even when United players were virtually camped in their own box.
In the absence of Ander Herrera, he was a crucially ruthless influence in the middle of the pitch and added further weight to Mourinho’s argument for keeping him in the team.