Chelsea boss Graham Potter is unsure of Reece James' injury suffered in victory over Bournemouth on Tuesday.
It was an earlier-than-planned withdrawal for James, seven minutes into the second period, on his return from the knee injury that ruled him out of the England squad for Qatar.
The 23-year-old lay on the turf with his hands on his head before receiving treatment and eventually walking off unaided.
Potter later said: "I'm not sure on the state of the injury. Too early to say. You can see his quality. It's a blow for us. Fingers crossed. We'll see how bad it is."