Boasting three centurions is a scenario no Wallabies team has ever experienced before.

But when Matt Giteau and Stephen Moore join the 100 Test club in the quarter-final against Scotland, that's exactly what the Wallabies can call on in the clash on Sunday (Monday morning AEDT).

Giteau and Moore will become just the seventh and eighth players to reach the milestone in Australian rugby history.

What makes it even more special is that Adam Ashley-Cooper already has 111 caps and attack coach Stephen Larkham played 101 games for the Wallabies in his World Cup-winning career.

It's an unprecedented level of individual experience in a Wallabies' line-up, but Larkham says it's the blend of youthful enthusiasm with old heads that makes this team special.

Larkham is confident the Wallabies finally have the right mix of youthful enthusiasm and old heads as they set their sights on lifting the Webb Ellis Cup.

"There's a number of ways to look at experience. You've got Dean Mumm who hasn't got the same amount of caps but he's certainly played over here.

"And then you've your experience in terms of Test match caps. I think coming into the tournament we've got a really good balance of age and experience.

"It's not just a team that's a little bit older and therefore more experienced. I think we've got the right number of experienced guys, the right number of older guys and the right number of younger enthusiastic guys."

Larkham still remembers the "fat-faced" kid with blond tips in his hair that set world rugby alight and 13 years later he hailed Giteau's Wallabies return as the World Cup stabiliser.

The personal milestones are being pushed aside as the Wallabies focus on keeping their World Cup campaign alive in a do-or-die match at Twickenham.

But the significance of Giteau's century looms as an ARU masterstroke that could deliver World Cup success in the coming weeks.

Giteau got a second lease on his international career after the ARU backflipped on its eligibility protocols earlier this year, making changes so overseas-based players who meet certain criteria are available for Wallabies selection.

The change has been dubbed "Giteau's Law" and the Wallabies are already reaping the rewards of a new selection era.

Giteau and Drew Mitchell were given Test lifelines while Kane Douglas, Dean Mumm, Israel Folau and Bernard Foley are all benefiting from new flexible contract situations.

Larkham played alongside Giteau in his Wallabies debut at Twickenham in 2002 and helped usher him into a championship-winning ACT Brumbies side.

"When [Giteau] came into the Brumbies for the first time he had a little fat face and had his blond tipped hair, he was straight out of school and looked about 12. He had two different coloured shoes on," Larkham grinned.

"I was aware what was going on [with the eligbility changes this year] … looking at [Giteau and Mitchell], their communication in the back line is certainly giving us a lot of stability.

"In the forward pack there are good, tough heads [in Mumm and Douglas]. From an attacking and back line point of view, it's invaluable what Gits and Drew have brought in terms of communication."

Giteau was stranded on 92 Tests four years ago when he was overlooked by then-Wallabies coach Robbie Deans for the World Cup squad.

But his form in France with Toulon prompted an ARU re-think and a rule change that could turn the Wallabies into World Cup contenders.

Now he becomes one of eight Wallabies players to reach 100 caps, joining Moore, Ashley-Cooper, Nathan Sharpe, George Gregan, George Smith, Larkham and David Campese – to have achieved the feat before.

Moore declared any celebrations would be postponed to ensure the team was focused on beating Scotland and advancing to the World Cup semi-finals.

"I probably had a bit more hair back then," Moore laughed when asked if he remembered his 2005 debut.

"I think for me it's not really a week to be reflecting on things, we've got a great opportunity to play in a quarter-final of a world Cup and that's more than enough to play for.

"I don't want the boys thinking about anything other than the opportunity we've got, preparing really well and playing our best rugby on the weekend because we know we're going to need to do that against Scotland."

Giteau is returning to the venue where he launched his Test career more than a decade ago.

If the Wallabies continue their outstanding form, it could also be the stage for his first World Cup triumph.

"I certainly remember [my debut at Twickenham]. We lost by a point and I went on with eight minutes to go," Giteau said.

"At the time [coach] Eddie Jones had a score system where everything positive you had a point, anything negative you lost a point.

"I think I was the only player to finish the game on minus four or something. After that game I never thought I'd get to 100 [Tests], no way. I didn't think I'd get past one."

WALLABIES CENTURIONS

George Gregan 139

Nathan Sharpe 116

George Smith 111

Adam Ashley-Cooper 111

Stephen Larkham 102

David Campese 101