Sky Sports reporter claims Raphael Varane could miss extended period through injury
Varane suffered the injury during United's 3-2 win against Nottingham Forest on Saturday, and had to be withdrawn from play at half time.
The Frenchman's injury adds to a growing list of defensive concerns for manager Erik ten Hag, with left-backs Luke Shaw and Tyrell Malacia both currently recovering from injuries.
Despite injury concerns of his own last season, however, Varane has started each of United's first three Premier League games, scoring against Wolves on the opening week of the season.
But the former Real Madrid star could be set for another extended period on the sidelines, according to Sky Sports reporter Kaveh Solhekol.
Man Utd sweat on Raphael Varane fitness
Solhekol has reported that Varane could miss up to six weeks of action following his injury against Forest.
He adds that United have decided to keep Harry Maguire at the club, despite interest from other clubs, due to the injury, meaning the England international could make a surprise return to the side while the Frenchman recovers.
Maguire has been an unused substitute for fixtures against Wolves and Forest this season, while he missed the 2-0 defeat to Tottenham through injury.
It was Victor Lindelof that was preferred by Ten Hag as Varane's replacement at half time against Forest, with Maguire remaining on the bench.
Solhekol explained: "As far as Harry Maguire's concerned, he is not going to West Ham. One of the reasons, we are being told, is because of the injury to Raphael Varane.
"He could potentially be out for up to six weeks, which would make it clear why United wouldn't want to let Harry Maguire go, especially on loan."
United have been linked with a move for a centre-back, with reports in France last week claiming that they were closing in on a deal for Nice defender Jean-Clair Todibo.