Chelsea manager Graham Potter says captain Cesar Azpilicueta is "conscious" and "speaking" in hospital after suffering a head injury during Saturday's home defeat by Southampton.
Azpilicueta lay motionless on the pitch after being struck in the face by Sekou Mara as the Saints substitute attempted an overhead kick.
Mara looked shaken as players from both teams and medical staff rushed to the 33-year-old defender's aid at Stamford Bridge.
Azpilicueta received oxygen treatment for several minutes before being stretchered off, though he was conscious as he left the field.
"It was a bad moment for us," Potter said.