Manchester City midfielder Fernandinho is unsure of the severity of his knee injury as he prepares to undergo a scan on Thursday.
The Brazil international, 33, came off in the second half of City's 2-0 derby win over Manchester United that returned them to the top of the Premier League table.
Already without the injured Kevin De Bruyne, City could now lose Fernandinho with four games remaining in their season.
Fernandinho said he would have to wait for the results of a scan to know the severity of the injury scare.
"We will see tomorrow [Thursday]. We are going to make the scan and we will see. I will talk to the doctor and he will make the best decision for everybody," he said.
"When I blocked the shot from Paul [Pogba] I felt my knee. It twisted a little bit. I could continue playing but I came off. That's what it is."
City are a point clear of Liverpool with three league matches remaining, the first of which is a trip to Burnley on Sunday.