Sunderland boss Gus Poyet says defender Anthony Reveillere is facing three to four weeks on the sidelines.
Reveillere, 35, injured a muscle between his Achilles and calf during the warm-up for Sunderland's derby clash against Newcastle on Sunday.
Poyet said the club had initially feared the problem was more serious, but the former France international will still be out for up to a month.
"It's a muscle injury," Poyet told a news conference. "We thought it was more because of the way it was translated...
Sunderland head coach Gus Poyet knows exactly what Hull counterpart Steve Bruce is going through as the Tigers boss attempts to drag his club out of an alarming slump.
The two men will go head to head at the Stadium of Light on Boxing Day, but will do so having experienced markedly different emotions in recent weeks with Poyet still basking in the glory of Sunday's derby victory at Newcastle and Bruce by contrast presiding over a team which last collected three Barclays Premier League points on October...
After November ended with a thoroughly deserved goalless stalemate against Chelsea, Sunderland boss Gus Poyet acknowledged that December was a month of crucial importance from which wins, not more draws, were needed.
As he prepares to follow the dramatic, morale-boosting victory at Newcastle with a Boxing Day home tie with Hull City, he is on course to achieve his wish.
The four games so far in the pre-Christmas fixtures list have produced one win and two draws, a run marred only by the 4-1 lesson...