Duncan Watmore will be sidelined for another two to three weeks after suffering a recurrence of the thigh injury which has ruled him out since the opening day of the season.
The winger had been set to make his comeback in Sunderland's Carabao Cup win at Burnley on Wednesday but was forced to pull out of the game after suffering the setback on the eve of the game.
And Jack Ross says Watmore now faces another few weeks out of action.
"Duncan was scheduled to play on Wednesday but suffered a recurrence of his injury post-training on Tuesday, so he will remain absent," said Ross.
"It's unfortunate for him, and he will be out for another two or three weeks."
Ross is hoping to have frontman Marc McNulty available for Saturday's trip to Peterborough United, with the on-loan Reading man having recovered from the hamstring problem he picked up in the win over Portsmouth a fortnight ago.
But Chris Maguire , who scored a hat-trick against AFC Wimbledon last weekend, is an injury doubt for the visit to London Road after picking up a knock although he will be assessed again on Friday before Ross makes a call on his fitness.
Ross said: "Marc trained today but Chris didn't train because he has a slight knock.
"We made eight changes for the cup game but all of those who did not play, with the exception of Chris, were only rested and will be available.
"We will see how Chris reacts over the course of this evening and then make a decision on him tomorrow morning."
Sunderland's only other injury absentee is midfielder Ethan Robson , who is still working his way back from a thigh injury.
