Chelsea keeper Petr Cech has undergone surgery for a depressed fracture of the skull after he was injured during the Blues' 1-0 win at Reading, BBC reported on Sunday.
The 24-year-old collided with Reading's Stephen Hunt in the first minute of the game at the Madejski Stadium on Saturday.
Cech was transferred to the Radcliffe Infirmary's specialist neuro-surgical unit in Oxford on Saturday night.
"The operation was successful but it is too early for an accurate assessment of his condition," said a Blues statement.
Cech and his replacement Carlo Cudicini were both carried off during the game and were both immediately taken to hospital.
Cudicini was discharged on Saturday night after being knocked unconscious in injury time.
Blues boss Jose Mourinho said immediately after the game that he was deeply unhappy with Hunt's challenge and said Cech was "lucky to still be alive".
The Chelsea statement continued: "Chelsea have reviewed the video of both incidents.
"We endorse the post-match comments of Jose Mourinho regarding the seriousness of these incidents.
"Chelsea will be writing to the Football Association with our observations."
Source: Xinhua