Jose Mourinho's decision to substitute Marouane Fellaini seven minutes after bringing him on was a big talking point following Manchester United's 2-0 defeat to Tottenham on Wednesday.

It turns out the Belgian had picked up a knock on the pitch, but it still managed to sum up the messy state of United's performance at Wembley.

Defensive errors cost the Red Devils as Spurs took a 2-0 lead within 30 minutes, courtesy of Christian Eriksen's opener after 11 seconds and Phil Jones' comical own goal.

Mourinho has since confirmed Fellaini could be out for anywhere between two to five weeks with ligament damage in his knee.

"He came off because he had something in his knee," said the Portuguese. "Unlucky for him and unlucky for me. He came on with enthusiasm, but he has an injury in his ligament.

"Two, three, four or five [weeks], I cannot say at the moment. I think I was unlucky with Fellaini as I wanted to change a little bit the dynamic of the team.

"After a couple of minutes, he was injured. I don't think it's a big, big thing but he was immediately feeling something and telling us he couldn't carry on."

Fellaini's injury comes at a time when his future at United is in doubt. The 30-year-old's contract expires this summer and he rejected a new deal in November.

It's being reported that Fellaini wants a huge pay rise worth £120,000-per-week to stay at Old Trafford which, naturally, has sparked outrage amongst fans.

Fellaini hasn't exactly been a hit at United since joining from Everton in 2013, yet he's making demands like he's indispensable at the club.

Speaking ahead of the weekend's action, Mourinho revealed he spoke to Fellaini about his contract situation after the Tottenham defeat and game him something of a reality check.

According to Mourinho, he told the Belgium international to "sign the contract and shut up" rather than take a gamble and keep demanding higher wages. He said:

"I told him yesterday: 'Sign the contract and shut up.' I told him: 'Don't gamble too much. Sign the contract before you know the extent of the injury.'"

Mourinho spoke the minds of many United fans with his comments and also confirmed Fellaini hasn't suffered Anterior Cruciate Ligament (ACL) damage.

"It is not an ACL, a complete rupture of any structure of the knee," Mourinho added, "but we need him.

"The Champions League is arriving [on February 21] and lots of tough matches to play and probably we are going to lose him for a few weeks."