London - Reigning Six Nations champions Wales have suffered a setback when back-row forward Ryan Jones withdrew from their squad on Monday with a hamstring injury.
Jones suffered the injury in the Ospreys' European Cup defeat by Irish province Leinster on Friday and has been replaced in the Wales squad by club-mate James King.
"Wales have released Ospreys back-row Ryan Jones back to his region due to injury, a Welsh Rugby Union (WRU) statement issued Monday said.
"Jones met up with the squad this (Monday) morning as they began preparations for the forthcoming 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."
Former captain Jones, a veteran of 75 Tests, led Wales to the 2008 Grand Slam but has been hampered by injury this season.
His loss is particularly unwelcome for Wales coach Warren Gatland given he can also cover at lock.
Wales second row Ian Evans, who also plays for the Ospreys, is facing a possible ban for an alleged stamp against Leinster.
But Wales captain Sam Warburton, who has not played since the defeat by Australia in November due to a shoulder injury, is expected to be fit for the Six Nations opener against Italy in Cardiff on February 1.