Marouane Fellaini
Marouane Fellaini is part of a 13-man injury list that is set to miss United’s clash against FC Midtjylland in the Europa League on ThursdayGetty

Manchester United midfielder Marouane Fellaini has flown back to Belgium to undergo further treatment on his hamstring injury which he picked up ahead of their 2-1 loss against Sunderland at the Stadium of Light on 13 February. The midfielder joins a number of players already on the treatment table, but the extent of his injury is yet to be ascertained.

According to the Daily Mail, the Red Devils midfielder has been receiving treatment from the Belgium national team physio Lieven Maesschalck with the club fearing that he has suffered a minor tear in his hamstring, which will see him sit out for at least three weeks. The 20-time English champions are facing a major crisis and Fellaini's injury makes it 13 first-team stars currently out of action.

Louis van Gaal has been forced to call up youth team players to provide cover in the absence of the senior stars, and is facing an uphill task as United compete on three fronts. They are in danger of missing out on a place in the top of the Premier League, as they lag behind fourth placed Manchester City by six points with 12 games to go. They they also compete for the Europa League and the FA Cup with a victory in the former, being their best chance to make it into the elite European competition.

Fellaini's absence from the team was confirmed by the Dutch manager following their arrival in Denmark ahead of their last 32 Europa League clash against FC Midtjylland. The Danish team are reportedly known for their set piece prowess and the big Belgian midfielder's presence will be missed, with the manager raising the concern during his press conference.

"Fellaini has a muscle problem. That is difficult for him. Normally you don't have 13 injuries in your team. When you analyse the injuries it's ridiculous. They are all contact injuries and that's bad luck," Van Gaal said, as quoted by the Daily Mail.

"This team specialise in set-plays – 48 per cent of their goals have been from set-plays. We try to defend that but that is difficult when you have 10 centimetres to make up," the Dutch manager added.