Chelsea face an anxious wait on the fitness of John Terry after he departed Stamford Bridge on a stretcher during Sunday's 1-1 Premier League draw against Liverpool and will undergo an MRI scan on Monday.
Terry, 31, had headed Chelsea ahead after 20 minutes before suffering the knee injury during a nasty-looking collision with Liverpool striker Luis Suarez.
The former England captain was making his comeback for Chelsea after completing a four-match ban having been found guilty of racially abusing Anton Ferdinand, but it could be the beginning of a renewed spell on the sidelines.
After colliding with Suareze, Terry signalled to the touchline before receiving treatment and departing the pitch on a stretcher with his head in his hands.
Chelsea manager Roberto Di Matteo revealed the club did not know the extent of Terry's knee injury with the captain - returning after his racism ban - set for a scan.
Di Matteo told Sky Sports 1: "He has a problem with his knee and will have an MRI scan tomorrow. At the moment we can't say, we'll have to wait for the scan which will tell us the extent of the injury. He is certainly a player that is influential for us. We will miss him.
"I was concerned about his well-being. We just got him back into the team after the ban. It was great seeing him out there."
Brazilian defender David Luiz is already sidelined with a bout of tonsillitis, leaving Branislav Ivanovic and Gary Cahill as the club's only fit centre-halves.
Information from the Press Association was used in this report.