England flanker Chris Robshaw requires shoulder surgery that will rule him out of the Six Nations.
Harlequins on Monday revealed that the former England captain must undergo an operation that is expected to keep him out for 12 weeks.
The 30-year-old was injured during Quins' Premiership defeat at Worcester Warriors on New Year's Day and will be unavailable to Eddie Jones for England's defence of their Six Nations title.
Robshaw has been outstanding since Jones opted to strip him of the captaincy and appoint Dylan Hartley as skipper.
He played a key role in England's Grand Slam triumph last year and maintained those high standards on the successful tour of Australia.
Robshaw also started when England beat the Wallabies at Twickenham last month to extend their winning run to 14 matches, but he will play no part in the Six Nations.