Paul Lambert says Aston Villa midfielder Fabian Delph might need surgery on a shoulder injury suffered in training.
Delph fell awkwardly on Tuesday, two days after starting England's European Qualifier in Estonia, and Lambert initially described him as a doubt for Saturday's game against Everton.
But pressed on the severity of the injury, the Villa boss admitted his player might have dislocated the joint.
He said: "Yes, (it's) probably that. Whether it is enough to allow it to rest for a couple of weeks I don't know or if there is more to it. I am pretty sure the medical people will discuss that."
Asked if an operation was a possiblity he said: "That's the thing, we don't know. That will be left up to the medical people to see what is the best procedure for it.
"It was an awkward fall. No-one was near him. He fell on his shoulder. It is not always straightforward so we need to go and get it checked out."
Surgery would place in doubt Delph's availability for next month's European Qualifier against Slovenia, which is followed by a friendly against Scotland.