Everton midfielder Jean Phillipe Gbamin will be sidelined for at least eight weeks.
The Ivory Coast international recently returned from two career-threatening injuries which saw him sidelined for about two years.
But the 25-year-old injured his knee before Monday's clash with Everton.
"Gbamin doesn't need surgery but he will be out for at least eight weeks," said manager Carlo Ancelotti.
"The plan for him is to be back for the start of the new season."