Graham Kavanagh has been ruled out for up to ten weeks after undergoing further knee surgery.
The Sunderland midfielder has been dogged by problems this season and was sidelined for five weeks earlier in the campaign after a knee cartilage operation.
However, he continued to struggle after returning and a re-examination has confirmed the need for more surgery.
Black Cats boss Roy Keane has lamented the loss of Kavanagh and hopes the Irishman will learn from his mistake of rushing his return from injury.
"Kav's going to be out for between nine and ten weeks, he had a knee operation the other day," Keane told Sky Sports News.
"It's something Kav has got to learn, he probably came back too quickly from his other injury, we tried to hold him back but he took things into his own hands and he's paying for it now.
"Kav's very keen to get back and we're delighted with that kind of attitude but sometimes you've just got to give time time and I think he's probably just a bit impatient with that and he's paying for that now."
Meanwhile, Keane is delighted to have landed Trinidad & Tobago international Carlos Edwards from Luton.
Edwards has penned a three-and-a-half year deal at Sunderland after the two clubs reached an accord on a £1.4million fee.
"We've lacked somebody wide on the right and we're delighted to get him," Keane said.
"I met him the other day and he's enthusiastic and delighted to be coming to Sunderland and he sees it as a challenge in terms of trying to get us back in the Premiership and we're delighted with it."
Edwards has confirmed his international team-mate Dwight Yorke played a major role in luring him to the Stadium of Light.
He added: "Oh yes, he was on the phone saying to me what a great club it is and he said to me 'wait until you see the facilities', which when I did it blew my mind.
"For him to give that kind of recommendation for the facilities and the club speaks volumes really."