Tuesday 12 September 2017 16:55, UK
Sam Warburton is to undergo surgery following the recurrence of a long-standing neck injury.
Cardiff Blues said that former Wales skipper Warburton, who captained the British and Irish Lions in New Zealand this summer, faces up to four months out.
It means that Warburton will miss Wales' autumn Tests against Australia, Georgia, New Zealand and South Africa.
The Blues said that 28-year-old Warburton had "exacerbated" the injury in training this week.
Warburton had yet to make his first appearance of the season after a post-Lions break before returning to training.
Blues head coach Danny Wilson said: "It's a major blow for all concerned, it's a blow for Cardiff Blues and Wales. We all hoped he would be back playing soon.
"It is a long-standing issue that he has had. He gets pain and discomfort on and off.
"The feeling was that two months off would help it settle completely and do him a world of good.
"He came back feeling confident about it. He went through the protocols when he came back to training, and during the contact element, just on pads, it began to flare up again.
"We looked into it in more detail, and it has led to where we are.
"He is obviously extremely frustrated. He thought that after two months he would come back really fresh, and that is not the case, but this is the right thing for him to do.
"He is a very good professional, and I am sure he will apply himself to his usual standards."
Flanker 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 November 11, before hosting Georgia, then the All Blacks and finally South Africa on December 2.
Ospreys and Lions flanker Justin Tipuric would be the favourite to wear Wales' No 7 shirt in Warburton's absence.
The current recovery timescale, though, indicates that Warburton will be available for Wales' Six Nations campaign this season, which they kick off against Scotland on February 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.
