England and Saracens scrum-half Richard Wigglesworth has been ruled out for the rest of the season after undergoing knee surgery.
The 28-year-old damaged his anterior cruciate knee ligament during Sunday's LV= Cup clash with Exeter.
Wigglesworth, who was part of England's World Cup squad, will miss the whole of the 2012 Six Nations championship.
Director of rugby Mark McCall told BBC Three Counties Radio that Wigglesworth will be out for "seven to nine months".
"It's one of those horrible rugby injuries," added McCall. "He was operated on on Wednesday afternoon.
"He'll be out, I suppose, for seven to nine months.
"He's a player who has worked incredibly hard to get back into English contention and he did that because he deserved it.
"He's been brilliant for Saracens. I thought he was very good in England's World Cup warm-up matches and in the game time he got in the World Cup, and he came back confident and buzzing to play.
"Unfortunately these things happen. It's the first injury he's ever had, the longest he's been out is two weeks so we feel desperate for him but we know he'll bounce back."
Neil de Kock, who shares scrum-half duties with Wigglesworth, will be expected to fill the void, while youngster Ben Spencer, a summer signing from Cambridge, will be handed more first-team responsibility.