Sunderland will be without Luke O'Nien until the New Year after he dislocated his shoulder in the midweek draw against Burton Albion.
And leading goalscorer Charlie Wyke has also been ruled out of tomorrow's game against League One basement side Wigan Athletic at the Stadium of Light after he picked up a knee injury against the Brewers.
O'Nien suffered an awkward fall near the end of the game and was in some pain as he was substituted deep in injury time.
Caretaker-manager Andrew Taylor said after the match that O'Nien's injury looked 'nasty' and appeared to be a dislocation, and the club has now confirmed that that is the case.
O'Nien will have to undergo further tests over the next week to discover the full extent of the injury, but he is expected to be out until January at the earliest.
Wyke was substituted in the first half against Burton after he took a knock to the knee which immediately began to swell up.
There was no serious damage, but he will not be ready to return this weekend.
Striker Aiden O'Brien is also a doubt with an ongoing ankle injury.
But Sunderland are set to bring winger Aiden McGeady in from the cold, with the former Republic of Ireland international included in the matchday squad this weekend.
McGeady last played for Sunderland in November last year before he was discarded by manager Phil Parkinson, and was then allowed to join Charlton Athletic on loan in January
McGeady has been training with the U23s this season but, following Parkinson's sacking last weekend, the 34-year-old is now back in the fold.
McGeady last played a first-team game for Charlton in July, and he has struggled with injuries since.
His only match action this season so far came in an U23 game against Crystal Palace last month, when he played for an hour before being substituted.
