Sunderland boss Steve Bruce has revealed that Anton Ferdinand is likely to be sidelined for at least a month.
The 24-year-old centre-half suffered ankle ligament damage during Sunday's 1-0 defeat at Fulham after a challenge from Cottagers striker Erik Nevland.
It had been hoped that the problem was not as bad as first feared, but medical tests have confirmed that a lengthy spell of rest is required in order to make a full recovery.
The news comes as an untimely blow to Bruce, with the Black Cats having suffered back-to-back defeats, and he will now face an unwelcome selection dilemma when Portsmouth arrive on Wearside this weekend.
Bruce told the Sunderland Echo: "It's a nasty one for Anton.
"Nevland's body weight came down on the ankle when they went to ground and he's no chance of being ready for the weekend.
"He's got no chance for Saturday and it looks like it could be a month at least for him.
"It's disappointing for him and disappointing for me."
On a more positive note for Bruce, he has admitted that George McCartney and John Mensah could come back into contention for the Pompey clash following recent knocks.
"I'd rate George at no better than 50-50 at the moment," said Bruce.
"I'm not ruling him out, but it's his hamstring again and we have to be careful with him.
"John Mensah has a chance of making it for the weekend.
"The physios are working hard on all of the lads; they're earning their corn."