The 24-year-old Scarlets pivot will start only his fifth test in the biggest match of his career on Sunday in the absence of clubmate Stephen Jones, who is sidelined with a back injury.

Wales coach Warren Gatland, who announced his team Friday, has decided to against moving James Hook from fullback to flyhalf, leaving the versatile Perpignan player to lead the attack as part of a dangerous back three.

“We’ve been really impressed with Rhys in the first couple of (warmup) games and we just felt that combination with James at 15, the confidence of having two attacking players at first receiver ... gives us that opportunity,” Gatland said.

Hook will retain the goal-kicking duties, hoping to add to his 303 points from 54 tests.

Gatland said he had full confidence in Priestly’s ability to step up to the task he had been given of guiding Wales in its critical Pool D match against the defending world champions. With 22-year-old captain Sam Warburton, he forms part of a very young brainstrust at the heart of the Welsh team.

“He has confidence for a youngster,” Gatland said. “He stays square, he’s not afraid. I think he has a very good balance in his game and he can give his outsides an opportunity to grab a bit of space.

“He does run, he’s an effective runner. He’s got a good boot on him and he’s got the classic confidence and cockiness of an outside half who has a bit of self-belief, and that’s what you’re looking for as a coach. I think he’ll do a good job for us.”

Gatland has also favored Luke Charteris in the second row ahead of Bradley Davies, who played at lock throughout Wales’ Six Nations campaign this season.

“It was a close call between the two,” Gatland said. “I think if we were picking the three second-rowers at the moment, I think Luke is our No. 1.

“He played really well against England and you can look at the things we’ve asked him to improve on in terms of height at the breakdown, contact area. He’s in great shape and he brings us some definite height. Just the way he’s improved in the last few month has been outstanding.”

South Africa announced its lineup earlier Saturday, revealing a team with a total of 815 test caps, the most experienced in its history. Gatland acknowledged that experience but said his lineup, with its 496 caps, would measure up.

“That’s definitely their strength, their experience, and they rely on that and are a tough team to beat,” he said. “It does help having some experience. I think we’ve got a nice mix of some talented youngsters with some experience as well.”

Gatland noted South Africa’s decision to name five forward as reserves, including three front-rowers, and said the battle of the benches would be a key part of Sunday’s game.

“I think that’s a key when you see South Africa’s bench and you see how strong that is and how they’re able to change a game,” he said. “In the past when we’ve been up against South Africa, if we’ve been winning the game they’ve been able to have a positive impact off the bench, and we’ve got to make sure we’re able to match that.”

The five-two split on the Springboks bench spoke of their strengths, Gatland said.

“They did that in the last game, didn’t they?” he said. “It’s fairly obvious which way they’re going to play the game. They’re going to take us on up front, which is very similar to what we expected and it was effective in the last game against the All Blacks.

“They want to dominate you physically.”