Manchester United expect to be without right-back Aaron Wan-Bissaka for 'several weeks' after he picked up an injury late in the 3-1 defeat to Brighton & Hove Albion.
Having started the team's first four games, Wan-Bissaka dropped to the bench against Brighton after battling illness during the week, but he managed to come on for the final five minutes of the game at Old Trafford.
During that brief cameo, Wan-Bissaka picked up a hamstring injury which United have revealed will keep him sidelined for several weeks, though speculation suggests he could be ruled out for as long as two months.
With a potential return date in mid-November, Wan-Bissaka could miss as many as seven Premier League games, including the Manchester derby on 29 October, as well as the team's first four Champions League group games.
United kick their European campaign off against Bayern Munich on Wednesday, with Diogo Dalot now expected to start.
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Manager Erik ten Hag is battling a major selection headache as Wan-Bissaka becomes the third full-back to pick up an injury.
Left-backs Luke Shaw and Tyrell Malacia are both sidelined, with Dalot often filling in on the left, but summer signing Sergio Reguilon now appears set for a significant run in the team as United battle a hectic run of fixtures.
Goalkeeper Tom Heaton remains sidelined alongside midfield duo Kobbie Mainoo and Mason Mount, while winger Amad Diallo is also out through injury.
Ten Hag is also without Antony and Jadon Sancho. The former is in Brazil battling assault charges, while Sancho has been banished from the first team after refusing to apologise for his social media post slamming the boss' treatment of him.