Sunderland boss Roy Keane has confirmed that striker Kenwyne Jones will see a specialist on Tuesday to determine the extent of his knee injury.
The powerful Trinidad and Tobago international, who recently returned to action following serious knee ligament damage, suffered the setback in training on Friday.
Jones missed the 2-1 loss against Portsmouth last Saturday and has now been ruled out of Wednesday night's Carling Cup clash versus Blackburn Rovers.
Keane said on Sky Sports News: "Kenwyne had a scan yesterday and he is going to see a specialist today. We'll have a better idea (of the full extent of the injury) this evening.
"It was a big blow for us to lose him on the Friday, just before the big game on the Saturday. But fingers crossed it is not too serious.
"Until he sees the specialist I don't want to be second guessing. It is the same knee. We want to make sure that it is not too serious.
"We are being tested at the moment in terms of the strength of the squad. We can't take any risks with the players."