Aaron Wan-Bissaka receives treatment after colliding with an advertising board
After a promising first campaign under the Dutchman, a number of off-field issues at United have been compounded by poor performances and results on the pitch.
Saturday's meek 3-1 home loss to Brighton meant the Red Devils have lost three of their first five matches for the first time in the Premier League era.
United have been forced to cope with a lengthy list this season including Luke Shaw, Mason Mount and Raphael Varane.
Ten Hag dismissed the notion that United are in crisis ahead of Wednesday's tough Champions League group opener at Bayern Munich but he will now have to plan without defender Wan-Bissaka.
"Aaron Wan-Bissaka is set for a period on the sidelines after sustaining an injury during the closing stages of Saturday’s game against Brighton and Hove Albion," the club said in a statement on Monday.
"The right-back came on as an 85th-minute substitute, having started the game on the bench after battling illness during the week.
"Further assessment will be needed to determine how long Wan-Bissaka will be out for, but initial indications suggest it will be several weeks."
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