YOUTH AND EXPERIENCE: With Steve Hansen's All Blacks it pays not to make generalisations.

With Steve Hansen's All Blacks it pays not to make generalisations.

For instance, that just because they've got more centurions than some Roman legions, they're an ageing unit. Think again.

Actually they're getting younger – almost by the day. And that's thanks to an ever-increasing injection of talent from the very special group that was the 2011 world champion New Zealand under-20 team.

The touring All Blacks possess no fewer than nine graduates from that fine side, the fourth straight Kiwi team to claim the world title, but also the last.

They are: Beauden Barrett, TJ Perenara, Charles Piutau and Francis Saili in the backs; and up front Dominic Bird, Sam Cane, Steve Luatua, Brodie Retallick and Luke Whitelock.

It's not difficult to close your eyes and imagine a fair swag of them having big parts to play in the long-term future of New Zealand rugby.

When you consider that two others – giant prop Ben Tameifuna and bruising loose forward Brad Shields – are also knocking on the door of the national squad, that's an incredible wave of talent from one very special year.

They represent the youthful side of an All Blacks squad that also has four test centurions and several others moving fast towards that magic number.

Thanks to the young 'uns the average age of this all-conquering squad has dropped to about 25 or 26.

"Sometimes there's a group of players coming through that are pretty special," All Blacks assistant coach Ian Foster said.

"The under-20 programme for us is an important little step. When the boys come out of high school into the provincial academies, and then get rewarded into the under-20s, it's like their first real opportunity to get exposed to the high-performance side of New Zealand rugby.

"We enjoy exposing them to a pretty complete programme and that particular group blossomed in that environment."

Of that swag of 2011 talent, Retallick is the only one to have forged a regular starting spot, though Piutau, Barrett, Cane and Luatua are all making regular, and consistent, contributions in 2013. The remainder no doubt await their chances.

Cane, who has emerged as a viable backup to Richie McCaw on the openside flank, said he had sensed it was a special squad when they came together for the 2011 tournament in Italy.

"A few guys had already played Super Rugby at 19 or 20, and a lot of the starting team had played ITM Cup already. Probably the core group of us first met at New Zealand under-17s, through to the schoolboys, and by the time we got to the 20s we knew each other pretty well.

"It's great to have seen each other progress since we were 16 or 17, and to be here in the best team in the world and battling it out for an All Blacks jersey is awesome and makes you take a bit of pride and pleasure in seeing your mates come a long way," Cane said.

Piutau, naturally, had a great time in a team that loved to express itself.

"They always say a few players go through to become All Blacks, but they probably wouldn't have thought this many would have made it," he said. "It's really cool just to see the same faces you came through the grades with."

Piutau may get the chance to figure in the All Blacks' tour finale against Ireland on Sunday (early Monday, NZ time) after starting all three of the previous tests on tour.

It doesn't look as if Hansen will veer too far from the two injury-enforced changes he has to make, and a tweak at hooker that looks likely.

But regardless, Piutau says it's been a year where he's grown up a lot, both on the rugby field and also as a young man fast becoming a role model for the next wave of young talent coming through the New Zealand system.

That's been helped by stepping into an All Blacks environment that doesn't just welcome its young players, but nurtures them.

"For me growing up and watching Richie [McCaw] and Dan [Carter], seeing them on TV, and now they're team-mates," Piutau said. "You don't really know how they'll be as people, but they're probably the most down-to-earth guys I've met, and everyone else in the leadership group has made that transition easy for me.

"I've grown a lot as a person, and learnt from everyone around me."

It's all part of what makes these All Blacks of 2013 pretty damn special. For every battle-hardened centurion, there's plenty of young foot soldiers read to follow them into battle.