Nemanja Vidic was taken to hospital after he was involved in a collision with Manchester United teammate David de Gea at Old Trafford on Sunday.
The Serbian managed to walk from the pitch but did not return after half-time and was subsequently taken to hospital because of the head injury.
After the match, United boss David Moyes admitted he didn't know much of Vidic's situation but said the club would find out more in due course.
"He has gone to hospital, I have only just seen him myself and I didn't see how bad it was from the touchline, but it was a terrible clash," Moyes told Sky Sports.
"It was an accident but hopefully he will be okay, I will find out more from the medics later on."
