Wales have been hit by an injury blow after back-row forward Ryan Jones was withdrawn from their RBS 6 Nations squad due to a hamstring problem.
Jones suffered the injury in his region's Heineken Cup defeat to Leinster on Friday night and, having been replaced in the squad by Ospreys team-mate James King, is set to miss Wales' defence of their title.
A Welsh Rugby Union statement read: "Wales have released Ospreys back-row Ryan Jones back to his region due to injury.
"Jones met up with the squad this morning as they began preparations for the forthcoming RBS 6 Nations and has been ruled out with a hamstring injury.
"Jones' regional team-mate James King, who made his debut for Wales last summer in Japan, has been called into the squad."
Jones, 32, has won 75 caps for his country and captained them to Grand Slam success in 2008, but has been hindered by injury this season.
His loss adds to Wales head coach Warren Gatland's concerns, with Ian Evans facing a possible ban.
The Ospreys lock was sent off for alleged stamping against Leinster and will face a disciplinary hearing.
Captain Sam Warburton has not played since the autumn defeat to Australia due to a shoulder problem, although he is expected to be fit for the tournament opener against Italy, while prop Gethin Jenkins is recovering from a leg injury.
Hooker Richard Hibbard is also nursing an injury after hurting his hip during the Ospreys loss in Dublin.
Centre Jonathan Davies is making good progress in recovering from a pectoral injury but still looks set to miss the opening two games against Italy and Ireland as Wales look to become the first side to win three outright titles in a row.
In addition to the call-up for King, who can play in the second row as well as the back row, two players will train with the squad from Tuesday in the form of Newport Gwent Dragons hooker Sam Parry and Scarlets second-row Jake Ball.