Goalkeeper Petr Cech has undergone surgery for a depressed fracture of the skull after he was involved in a sickening clash in Chelsea's victory over Reading.
Cech was stretchered off the pitch at the Madejski Stadium on Saturday evening after colliding with Reading's Stephen Hunt.
The Czech Republic goalkeeper was immediately taken to a local hospital, but was then transferred to the Radcliffe Infirmary in Oxford to the specialist neuro-surgical unit where the operation took place.
Chelsea claim the operation was successful but it remains too early to give an accurate assessment of his condition.
The club's official website also claims they endorse the post-match comments of Blues boss Jose Mourinho, who also lost Cech's replacement Carlo Cudicini towards the end of the match with a less serious head injury.
After the match, Mourinho said: "I have to wait and see what the Football Association will do about it and I'm also waiting to hear what the experts think of both incidents.
"Carlo, I think, was knocked out as a consequence of the way he hit the ground, but a knee coming at Petr like that, at such speed - the boy was even laughing afterwards.
"It was unbelievable and players should respect each other more than that."