The Red Devils are looking to send Mourinho’s second season at Old Trafford with some silverware despite a disappointing Premier League campaign.
Manchester United are in second place in the table but a staggering 13 points adrift of Premier League champions Manchester City.
Mourinho led the Red Devils to the Europa League and the League Cup in his first season in charge of the 20-time English champions.
Spurs could have a slight advantage considering the north London side have been playing their home games in the Premier League at Wembley this term.
Furthermore, Tottenham were impressive 2-0 winners against Manchester United in the Premier League at Wembley earlier this year thanks to Christian Eriksen’s second-minute goal and Chris Smalling’s own goal.
Former Arsenal star Merson is backing Mourinho to mastermind an important win on the big occasion against Spurs at Wembley on Saturday afternoon.
“This one is a massive match because I don’t know where these two teams are going if they lose this one. There will be a lot of questions for whichever team loses this game,” Merson told Sky Sports.
He added: “I’m going to favour United here because Jose Mourinho gets the tune in big football matches, and Spurs haven’t really done that.”
Manchester United signed Chile international Alexis Sanchez in a swap deal from Arsenal in the January transfer window.
The Red Devils forward has only managed to score two goals in 14 games to prompt criticism of his form.
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