Sunderland forward Duncan Watmore has suffered a suspected cruciate knee ligament injury and is set to undergo surgery later this week once scans have been undertaken.
The 23-year-old was substituted shortly before half-time in Saturday’s 2-2 home draw against Millwall is to have an exploratory operation later this week to confirm the extent of the injury.
Watmore only returned on September 30, after 10 months out with a torn anterior cruciate ligament in the same left knee that has been damaged this time.
He has made six appearances and after the Millwall game, and new boss Chris Coleman said: “We have to get the clinical results to find out exactly what he has done.
“We haven’t got those yet, so everybody is looking at it and suspecting, but we don’t know yet.
“Of course we are worried because of what happened before, but until we get a definite we can’t really say what is what.
“Duncan worked so hard to get back. He’s a real good player and an even better guy.”