• Prop and fly-half will definitely miss trip to Ireland • Jenkins could be out for four to five weeks

Wales will be without the prop Gethin Jenkins and the fly-half Rhys Priestland for the start of the Six Nations.

Both players are suffering from knee injuries and will miss the opener against Ireland on Sunday week, with Jenkins at risk of missing a lot of the Championship.

Warren Gatland, the Wales coach, said: "Gethin is struggling and could be out for four to five weeks. Rhys will be struggling for the first game. We're assessing him day by day."

The flanker Dan Lydiate is a doubt for the trip to Lansdowne Road because of an ankle problem, but the prognosis over the centre Jamie Roberts's knee injury is more positive.

Gatland, speaking at the Six Nations launch in London, said: "Dan Lydiate is touch and go. We're hoping Jamie Roberts will be OK."

Gatland said the absence of the Lions front-row Jenkins and Priestland, who emerged as one of the stars of last year's World Cup, will be keenly felt. "Gethin is a huge loss for us for potentially the first two games of the tournament," he said. "He's been playing exceptionally well for the Blues in the last month.

"He's a world-class player. He's got a very good rugby brain and is able to assess things on the field. He's almost like a coach on the field. You get a lot of information from him at half-time, what's going right or wrong, tactically where we need to change.

"Rhys was probably the find, if not the best, fly-half at the World Cup. He really does fit the type of game we want to play. His kicking game and vision are excellent. He stretches opposition defences as well because he's not afraid to run.

"There's a very good balance to his game. You can't underestimate the space he created for our midfield at the World Cup. He was one of the reasons we saw some really big performances from Jamie Roberts, Jon Davies and Scott Williams. He will be a big loss for us.

"But there's experience to come in with James Hook and we may look at Gavin Henson in that position too."

Gatland said Leigh Halfpenny is likely to take over the kicking duties in Priestland's absence.