Leicester midfielder Wilfred Ndidi may need surgery and could be out for up to a month.
The Nigeria international was ruled out of the Foxes' English League Cup semi-final first leg with Aston Villa on Wednesday.
Boss Brendan Rodgers revealed Ndidi suffered an injury in training - although did not specify what - on Tuesday and may face an operation.
"Wilf took a knock in training yesterday, which unfortunately means he might need a slight operation tomorrow," he said on the club's Twitter on Wednesday.
"That'll put him out for a few weeks, but it's not overly serious, so hopefully, going into February, he'll be fit and ready to go again."
If Ndidi misses the rest of the month he will sit out five Leicester games - including their semi-final second leg at Villa on January 28.
Australian Associated Press