Martin O'Neill says midfielder Lee Cattermole has suffered an injury setback and is doubtful for Saturday's match at Wigan.
The 24-year-old has been out with a knee injury since November, but after good progress he made his comeback on Tuesday against Bolton in the FA Cup third round replay that the Black Cats ultimately lost 2-0.
However, on Thursday, the former England under-21 international received a fresh knock in training which looks set to rule him out of Saturday’s game against his former club Wigan.
O'Neill explained to reporters: "We have a number of injury problems ahead of the Wigan game, and I don't want to run through them.
"But Lee Cattermole had had a bit of a setback.
"He trained for the game yesterday – we were trying to get a bit more fitness into him and the new lads who have arrived – and he had a bit of a setback.
"We are hoping it's not as bad as before, but I would say he would be doubtful for tomorrow."