Rangers wanted to snap up McTominay on loan, as they felt he could offer them an increase in creativity.
However, Mourinho has decided to keep the 22-year-old at Manchester United rather than allow him to join the Ibrox side.
And Mourinho may regret that decision, as he only needs to look across the city to see just how important a loan move to Scotland can be to a player’s development.
Manchester City have formed a good relationship with Celtic over recent years, and have had great success loaning their prospects to the Glasgow side.
City have allowed Celtic to take the likes of Jason Denayer and Patrick Roberts on loan in recent times, and the pair have both developed as a result of their moves.
McTominay’s progress could also have been boosted by a switch to Scotland, as he would surely have played first-team football regularly at Ibrox.
But it seems Rangers will now have to look elsewhere, as they search for an injection of quality in the January transfer window.