Rugby World Cup 2011: Jamie Roberts backs James Hook as Wales 15

Wales centre Jamie Roberts tests the South Africa defence in Cardiff last year

Wales centre Jamie Roberts says that James Hook will always be a major influence on the team regardless of the position he is selected in.

Coach Warren Gatland has opted to put Hook at full-back for their World Cup opener against South Africa on Sunday.

That sees four-cap Rhys Priestland handed the pivotal number 10 shirt in the continued injury absence of British and Irish Lion Stephen Jones.

"It doesn't change the way we play at all," Roberts told BBC Sport Wales.

"James is going to be a huge threat wherever he plays in the backline and certainly at full-back he's shown his capability there before.

"His kicking game is going to be hugely important to us come Sunday and... I think it's predicted rain now, so that's going to change the way things are completely but we'll see.

"I think Rhys has shown his ability at 10 and is more then capable of handling the pressure."

Jones, who has won 100 caps for his country, missed all three of Wales' warm-up Tests with an ongoing calf problem, with forward Ryan Jones and prop Gethin Jenkins also afflicted with similar injuries.

A fit and in form Lee Byrne has in the past been Wales' default selection at 15, but the Clermont Auvergne player was limited to just 58 minutes in the win over Argentina as he returned to action after a knee injury.

That has seen Gatland opt for the combination of Hook at 15 and Priestland at 10 which started the 19-9 win over England in Cardiff.

"We are trying to get one of our best players on the field in James Hook," said Gatland.

"There was a comment from [former Wales captain] Gwyn Jones a few weeks ago when he said James was probably the best Welsh 10, the best Welsh centre and the best Welsh full-back.

"We were really impressed with Rhys in the first couple of warm-up games [against England], and we felt that combination with James at 15 and having two attacking players at first receiver - with James being able to do that as well - gives us an opportunity.

"Rhys has confidence, he has got a very good balance in his game. He is an effective runner, has a good boot on him and he has that self-belief you look for as a coach."

Wales have only beaten South Africa once, in a warm-up game in Cardiff before the 1999 World Cup, although they have come close in several of their recent encounters.

Wales have been able to match the Springboks in fitness and physicality, and have out-scored the defending world champions in tries scored.

But Roberts, who locked horns with them during the 2009 Lions tour, says that South Africa's kicking game is second to none and they must deal with that in Wellington.

"Certainly the way South Africa play, their kicking game is one of the best in the world, their kick-chase game is spot-on and we've worked very hard on that this week," Roberts added.

"It's just doing the basics well: territory and securing set-piece, two words that are chucked out there but are so crucial against South Africa.

"Whether they kick the ball long and we return the ball into touch and they make yardage, or they put the ball in the air and compete to win the ball they certainly make huge territory gains.

"Set-pieces are also going to be vital. Scrum and line-outs, South Africa base a lot of their game around that and certainly we've worked very hard on that.

"It's been a long week, the week has taken ages just building up to the game.

"It's a huge game, it's probably the biggest game a lot of us boys have been involved in in our careers and it's one I'm massively looking forward to.

"We're just waiting for the game to come now, it's been four years in the waiting for this World Cup and all of a sudden it kicks off at the weekend and it's so exciting.

"The place has just gone rugby crazy."