British & Irish Lions and Wales captain Sam Warburton will miss the remainder of the year to undergo surgery on a long-standing neck injury.
His club, Cardiff Blues, announced in a statement that Warburton 'exacerbated the injury' in training this week.
The operation will see Warburton miss Wales' internationals in November against Australia, Georgia, New Zealand and South Africa.
Warburton has played 74 times for Wales and led the Lions on their last two tours -- Australia 2013 and then New Zealand.
His absence is a huge blow for the Blues and Wales, with Warburton set to have been a key part of national head coach Warren Gatland's Test plans in November and December.
Wales launch their autumn series against the Wallabies in Cardiff on Nov. 11, before hosting Georgia, then the All Blacks and finally South Africa on Dec. 2.
Ospreys and Lions flanker Justin Tipuric would be the clerar favourite to wear Wales' No. 7 shirt in Warburton's absence.
The current recovery timescale, though, indicates that Warburton will be available for Wales' RBS 6 Nations campaign this season, which they kick off against Scotland on Feb. 3.
For the Blues, Warburton's absence comes after they recently lost the services of his fellow flanker Ellis Jenkins for up to 12 weeks because of a serious hamstring injury.
Warburton has undergone a handful of operations during his career, and the latest setback means he is denied an early rematch against New Zealand following the Lions' exploits.
A catalogue of previous injuries include a dislocated shoulder, torn hamstring, ankle ligament damage and fractured cheekbone, but he has always returned from such blows and maintained world-class form.
Warburton's loss from the autumn games could leave Gatland facing close assessment of his back-row resources.
While No. 8 Taulupe Faletau has been performing superbly for Bath this season, Gloucester's Ross Moriarty has yet to return from injury and seasoned Ospreys campaigner Dan Lydiate has been recovering from knee ligament damage suffered late last year.
Openside flanker specialist Warburton has also filled the blindside role on a number of occasions for Wales, but that option has now been lost to Gatland as he looks ahead to the autumn fixtures.
The Blues, meanwhile, lost their opening two games in the Guinness PRO14, while a European Challenge Cup campaign that begins next month has seen them drawn in the same pool as Toulouse, Lyon and Sale Sharks.