Newcastle utility man Ryan Taylor is facing up to 12 weeks on the sidelines after undergoing surgery to repair ankle ligament damage.
Manager Chris Hughton revealed last Thursday that Taylor had suffered an ankle injury in training, but the extent has only just been revealed.
He underwent surgery on Monday and is expected to be out of action for up to three months.
Hughton said: "It's very disappointing to lose Ryan for this period of time.
"Although he hasn't played as much football as he would have liked, he has been a very valuable member of our squad this season."
It is understood that Taylor was injured in a challenge with team-mate Sol Campbell.
The 26-year-old has made only four appearances to date this season, with his three starts all coming in the Carling Cup.
However, his ability to play at both right-back and on the right side of midfield means his loss until well into the new year will deprive Hughton of the services of a very useful back-up player.
Taylor's misfortune is the latest to hit the Magpies, who already have loan signing Hatem Ben Arfa on the long-term casualty list with the double leg fracture he suffered at Manchester City on October 3.
In addition, first-choice keeper Steve Harper is only now approaching full fitness after shoulder surgery which has kept him out since the middle of the previous month, while Dan Gosling is yet to play since his arrival from Everton as he battles his way back from a serious knee injury.
Striker Shola Ameobi missed last Saturday's 0-0 Barclays Premier League draw with Fulham as he recovered from a hamstring strain, and in the circumstances, the Magpies' concerns over Andy Carroll making his England debut tonight despite reporting with a groin problem are perhaps understandable.
The Newcastle squad was pruned severely in the wake of relegation to the Championship and although Hughton has been able to strengthen since, there is not a great deal of top-flight experience outside of the core of his first-team regulars.