Saracens and England scrum-half Richard Wigglesworth has been ruled out for the rest of the season after undergoing knee surgery.
The 28-year-old suffered the injury during his club's LV= Cup victory over Exeter, being forced out of the action just 20 minutes into his return from the World Cup.
And subsequent tests have revealed that Wigglesworth has damaged his anterior cruciate ligament and will not be able to play for the rest of the campaign.
"It's a big blow for Wiggy who has been playing so well for Saracens and has worked so hard in the past 18 months to get himself back in the England side," Sarries director of rugby Mark McCall told the club's official website.
"In my opinion he was one of England's stand out players at the World Cup and it's a shame he will miss the Six Nations.
"It's also a blow for us but we are lucky to have two very good players in Neil de Kock and Ben Spencer who have both performed so well this season and because of that, we are not looking to recruit."
As well as being ruled out of Saracens' Aviva Premiership title defence and Heineken Cup challenge, Wigglesworth will also miss the 2012 RBS Six Nations competition.