Gus Poyet believes that Anthony Reveillere could be set for a lengthy spell on the treatment table.
The French defender picked up an injury during the warm-up before Sunderland's match with Newcastle United on Sunday and the initial prognosis does not look good.
Reveillere was due to start in the North East derby, but began to feel pain in his calf prior to kick-off and Poyet thinks that the complaint could be a severe one.
“It looks very bad," the Uruguayan boss said to the Chronicle.
“Anthony went to have a check-up and a MRI and he will have another."
“It is not a normal injury when you can say he has pulled a muscle or had a problem with his achilles. He felt something really strange so we will wait and see.”
Thankfully for Sunderland, Reveillere's absence didn't cost the side too much on Sunday, as they were still able to pick up a 1-0 victory.
Sebastian Coates came into the side as a result of the experienced full-back's absence, with John O'Shea stepping out into the left-back slot.
The Black Cats defence coped admirably with the set-back, too, and they will feel very proud of the clean-sheet they achieved.
Sunderland are now up to 14th position in the Premier League and they will be looking to continue climbing up the table, even without Reveillere, in the upcoming weeks.