Sunderland will be without striker Stephen Elliott for up to two months after he damaged ankle ligaments during the 3-0 win at Leeds United on Wednesday.
The 22-year-old replaced David Connolly shortly before half-time at Elland Road and scored the Black Cats' third goal before twisting his ankle and limping off on the hour.
Connolly's thigh injury will prevent him facing Leicester City on Saturday, but Elliott's problem is more serious.
Manager Roy Keane told the club's official website: "Stephen is the worst of them, the worst-case scenario is that he'll be out for a couple of months.
"He's done the ligaments and jarred it, but there's no breaks or anything. He's had a sore one. We saw it on the camera after the game and it's quite nasty.
"It's disappointing for us and for him, after scoring a great goal."