Manchester United fear Luke Shaw could be out for the rest of the season due to a muscle injury sustained during the team's 2-1 win over Luton Town, a source has told ESPN.

Shaw started the game at Kenilworth Road on Sunday, but was substituted before half-time. The left-back was also substituted at half-time in the 2-1 win over Aston Villa a week earlier.

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After undergoing medical tests this week, there are fears that Shaw's leg injury could rule him out for months rather than weeks with the 28-year-old now facing a battle to return before the end of the campaign.

The club posted a statement on Tuesday that read: "Luke Shaw has sustained a muscle injury and will be out for an extended period. Further assessment is still needed to determine the severity but we expect him to be absent for a few months."

An extended absence would also make Shaw a doubt ahead of England's campaign at this summer's European Championships in Germany. It's another blow for United manager Erik ten Hag, who is also without centre-back Lisandro Martínez.

The Dutchman is short of options at left-back while Tyrell Malacia recovers from a knee injury which has prevented the 24-year-old from playing at all this season. Sergio Reguilón was signed on loan from Tottenham as cover, but his temporary spell was cut short in January and has since joined Brentford.

Centre-back Victor Lindelöf and midfielder Sofyan Amrabat have been used as emergency options at left-back this season while Diogo Dalot has also filled in.

Shaw has been restricted to just 15 appearances this season after missing three months between August and November because of a leg injury.

United are on a five-match winning run and are back in action against Fulham at Old Trafford on Saturday. Ten Hag's team also face Nottingham Forest in the FA Cup fifth round on Wednesday.