Victor Anichebe is being assessed today amid fears that he has suffered knee ligament damage.
The full prognosis is not yet clear with Sunderland's medical team establishing the extent of the damage.
Anichebe had only been on the pitch for a matter of minutes when he was hurt in a collision with West Brom's Claudio Yacob.
It appeared to be a contact injury, rather than a recurrence of the hamstring problem that kept him out of action in the aftermath of the 4-1 defeat to Burnley at Turf Moor on New Year's Day.
Anichebe continued in the game, but was clearly in some discomfort, limping in the immediate aftermath of the clash.
On Friday West Brom boss Tony Pulis, Anichebe's former boss, said the Nigerian was a 'good player on his day' but suggested injury problems were the reason for his exit from the club in the summer.
Sunderland will be despertaely hoping the damage is shown to be less severe than feared, with a crucial run of Premier League games on the horizon.
The Black Cats face Tottenham Hotspur on January 31st, before a massive game with Crystal Palace on February 4th. Southampton are the visitors at the Stadium of Light a week later.
Jason Denayer was also hurt in the same run of play on Saturday, and his progress is also being monitored.