Carlos Cuellar has picked up a hamstring problem which could keep him out of several Sunderland fixtures.
The former Aston Villa defender was substituted at half-time during the 1-1 draw with Liverpool at the Stadium of Light on Sunday, and now it seems that he could miss several upcoming games. He is almost certain to be unavailable for Sunderland's Saturday clash against West Ham, and could also miss additional fixtures.
Black Cats boss Martin O'Neill said: "He has had a hamstring problem so he will be very, very doubtful, not just for this game, but perhaps for the next couple of matches.
"From that viewpoint it is a bit disconcerting, but these things happen and you just have to get on with it."
Sunderland are also waiting on Adam Johnson, whose injury kept him out of both the fixture against Liverpool and the last England squad O'Neill added: ""We were hoping that he would have made the fixture against Liverpool last weekend, but that wasn't the case.
"He is progressing and it's too early to say about this weekend."