Wales head coach Warren Gatland has gambled on teenage duo Kristian Phillips and Tom Prydie and uncapped scrum-half Richie Rees in his RBS 6 Nations squad.
Ospreys duo Lee Byrne and Adam Jones both return to the 35-man squad after recovering from injuries picked up during the British Lions tour to South Africa.
With half-back duo Dwayne Peel and Mike Phillips among a host of injury victims Rees will compete with club colleague Gareth Cooper for the No.9 shirt.
Wingers Prydie, who at 17 became the youngest player in Heineken Cup history last month, and Phillips, 19, are in line to make their senior debuts, as is Saracens prop Rhys Gill.
“We are now at the beginning of our countdown to the World Cup and this slightly larger squad reflects that,” said Wales coach Gatland.
“We have brought in some youngsters to put some pressure on some of our senior players and to help increase the depth we have in certain positions.
“Kristian is a good example of an exciting young player, he has just won the Principality player of the month award and scored five tries in one match for Neath, he is skilfull and very quick.
“Elsewhere we are very happy to welcome back the likes of Adam (Jones) and Lee (Byrne) who were both obviously missed in the autumn, although at full-back in particular a certain James Hook provided more than ample cover.
“Our first match at Twickenham could set the tone for the Championship for both sides, we will both be desperate to win that first match.
“We then come to the Millennium Stadium for two home matches and the support we have there will make a huge difference to us."
The Ospreys (14) and the Blues (13) make up the bulk of the squad which will again be led by 2008 Grand Slam captain Ryan Jones.
The Scarlets provide four players – Matthew Rees, Jonathan Davies, Stephen Jones and Martin Roberts – the Dragons two - Luke Charteris, Dan Lydiate - with just two players based outside Wales in Gill and Sale’s Effion Lewis-Roberts.
Gareth Cooper, Bradley Davies, Leigh Halfpenny, Tom James, Gethin Jenkins, Deiniol Jones, Andy Powell, Richard Rees, Jamie Roberts, Tom Shanklin, Sam Warburton, Gareth Williams, Martyn Williams.
Huw Bennett, Dan Biggar, Andrew Bishop, Lee Byrne, Ian Gough, James Hook, Paul James, Adam Jones, Alun Wyn Jones, Ryan Jones, Kristian Phillips, Tom Prydie, Jonathan Thomas, Shane Williams.
Jonathan Davies, Stephen Jones, Matthew Rees, Martin Roberts.
Luke Charteris, Dan Lydiate