The club are to decide today whether the midfielder requires surgery on his left knee after being withdrawn after just seven minutes into his substitute appearance at Wembley. If so, the player could face the next eight weeks in recovery.
Speaking after Wednesday’s loss, United manager Jose Mourinho confirmed Fellaini’s injury: “He came off because he had something in his knee. He came on with enthusiasm, but he has an injury in his ligament.”
“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. It’s always the same thing. It is the lateral ligament. I don’t think it’s a big, big thing but he was immediately feeling something and telling us he couldn’t carry on.”
The 30-year-old damaged his medial collateral ligament during Belgium’s 4-3 win over Bosnia and Herzegovina in October of last year.
He later suffered complications upon his return to action at Chelsea a month later but struggled with the injury in subsequent fixtures against Newcastle, Basel and Brighton.
Fellaini missed a further six weeks of football after that and has managed just 45 minutes since returning on 5 January.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies