The Australian-born second-rower was stretchered off in the first half of Wales' scratchy 11-10 win over Fiji on Friday night. His hamstring was torn away from the bone in a sickening collision and he may not play again this season.
Wales coach Mike Ruddock confirmed: "The injury needs an operation and Brent is out of action for at least four months, possibly six.
"It's awful news for Brent and his family, as well as the Ospreys and Welsh rugby, who have lost a quality player.
"On the injury front, we are getting a lot more headaches than we would like."
Cockbain, who turns 31 on Tuesday, joins fellow British Lions Gethin Jenkins, Ryan Jones, Dwayne Peel, Tom Shanklin and Gavin Henson on Wales' ever-expanding injury list. As well, three other Wales players - Dafydd Jones, Kevin Morgan and Chris Horsman - limped off during the Fiji match with ankle injuries. Jones and Morgan are unlikely to play against South Africa next Saturday.
Wales 7s Manager Steff Thomas believes Luke Treharne has all the attriubutes to be a top class captain. WRU TV's Graeme Gillespie hears his reasons why as the squad prepare for the opening two legs of the new World Series in Dubai and South Africa.
The British & Irish Cup kicks off this weekend with the four Regional Premiership Select XVs flying the flag for Wales. Welsh
Sat 14 Nov: Blues Premiership Select v Nottingham (2.30) & Connacht Eagles v Dragons (2.30)
Sun 15 Nov: Yorkshire Carnegie v Ospreys Premiership Select (1.30) & Scarlets v Bedford Blues (3.00)
The Welsh Rugby Union is forming a new Youth Board with a brief to help keep more young people involved in the game during their late teenage years and beyond. The first task of the fifteen strong Board will be to analyse and consider the issues which lead to a number of youngsters drifting away from the sport between the ages of 16 and 21. To apply visit www.wru.wales/youthboard
The Foster's Challenge Cup will involve the 12 Principality Premiership sides and will run during European and British & Irish Cup weeks, providing vital fixtures for the participating clubs and an opportunity for upcoming players to step up to semi-professional rugby and make a claim for starting places within the Premiership squads.
Eighty schools and colleges in Wales now have a full time rugby officer as part of the WRU's school club hub scheme. All of the school club hub officers recently gathered at the National Centre of Excellence for various workshops.
With Liam Williams forced out of the World Cup through injury, lock Luke Charteris and Skills Coach Neil Jenkins say they have to put yesterday's defeat behind them as Wales now look ahead to another physical encounter against South Africa in the quarter-finals of the Rugby World Cup.
WRU Consultant Head of Physical Performance Paul Stridgeon praises the Physical Performance department for their work and dedication as he addresses the media ahead of Wales' Pool A clash against Australia
Twelve young people have been selected to follow a one year WRU Coach Core apprenticeship programme. Coach Core was set up by the Royal Foundation of the Duke and Duchess of Cambridge and Prince Harry as part of the Olympics legacy in 2012 and the Duke of Cambridge was on hand to meet the apprentices on their first day in the job. The programme has been funded by the Hunter Foundation.