Duncan Watmore looks set to miss the remainder of the Premier League season after suffering a cruciate ligament injury at the weekend.
The 22-year-old former Altrincham striker had to be stretchered off the field during Sunderland's 2-1 win over Leicester City on Saturday.
He collided with Christian Fuchs in the 83rd minute of the tie and now joins Paddy McNair and Lynden Gooch in the club's treatment room.
After the match, Black Cats boss David Moyes told Sky Sports: "It's his knee. We'll need to get it assessed properly and find out exactly what it is, but it doesn't look good for him at the moment.
"It doesn’t look great. Duncan has been playing well."
He added: "The good news is that he [Gooch] doesn’t need an operation. That’s the big news, his ankle will heal in time.
"But it’s still going to be an injury that keeps him out somewhere between eight and 12 weeks."