Manchester United midfielder Casemiro has been ruled out for "several weeks" with a hamstring injury, the club announced on Friday, adding to manager Erik ten Hag's woes.
After missing three matches, the 31-year-old captained Erik ten Hag's side on his return against Newcastle in the League Cup on Wednesday.
Casemiro was replaced at half-time of the 3-0 defeat and United have now confirmed he will miss a key run of fixtures.
The club said in a statement: "Casemiro will be out for several weeks due to a hamstring injury suffered during our Carabao (League) Cup defeat to Newcastle United on Wednesday.
"The Brazilian midfielder was withdrawn at half-time due to the issue, and subsequent assessment has revealed a strain that will keep him out for a number of weeks."
United are eighth in the Premier League table, with five defeats from their first 10 games and face a challenge to reach the Champions League knockout stages.
