RISING UP: Beauden Barrett's performances in the black jersey have emphasised New Zealand's depth at number 10.

Beauden Barrett, Steven Luatua, Wyatt Crockett and Charles Piutau epitomise a common strength.

Together, these All Blacks form a small sampler of the unrivalled depth New Zealand rugby has once again created.

Remember the concerns post 2011? The national fears about ageing veterans, who and how they would be replaced.

Credit must go to the All Blacks' nurturing process. Other than midfield, No 8, lock and hooker there are now more-than-capable alternatives - contingency plans - in every position for the foreseeable future.

Back-up is not a suitable term. Look no further than first five-eighth for proof. Barrett's extended cameo from the bench after replacing Dan Carter against the Springboks showcased all his calm, natural abilities that say he was born for this level.

"It's my personality but also nailing your preparation so you can take the field knowing you've done all the work. That way you can play with a clear head," Barrett said.

"It helps when you get game time. You have more opportunities to express yourself. I was reasonably happy. This is a different week, with different challenges over here. If I have to [start] I'll be ready."

There is a suspicion Barrett may develop into the premier long-term playmaker. In most other rugby nations he would start in Argentina this weekend. But with Aaron Cruden recovered from a knee complaint, Barrett is expected to slot back on the bench. And don't forget the presence of Tom Taylor, the fourth-choice pivot, on tour.

The first-five situation is identical to when Liam Messam displaced Luatua. The Blues blindside confirmed his talents with two athletic efforts against the Wallabies but, as has been the continued policy, the incumbent gets first dibs.

In June, it also seemed Crockett would overtake Tony Woodcock, yet the experienced loose-head has reclaimed his place.

Like Barrett and openside Sam Cane, Piutau was another to take his chance at Eden Park, chiming in from the back with aggressive carries and a heady kicking game.

When all are fit, halfback is a hugely competitive position. Then there's wing Cory Jane's pending return. The list goes on.

The secret to building depth is patience. The All Blacks prefer to ease their rookies into the test arena. It's a gradual, controlled progression. Competitors don't have that luxury. They face a risky sink-or-swim option.

"They don't like to rush you into it," Barrett said. "That's a good thing. Learning off ‘DC' [Dan Carter] and Cruden has been awesome. If I get the opportunity to play I feel ready."

Dane Coles is the classic case. Slowly he's nearing the head of the hooking queue, but there's been no pressure from within to reach that crescendo.

"It's good they've eased me in and now I feel comfortable in the side," Coles noted.

An inclusive, encouraging environment is another key factor. Respect for senior players is a given, but gone are the days of an elitist mentality.

"There's still the backseat thing. It goes on caps, but it doesn't feel like it in this team," Barrett explained. "It's pretty easy to come in and be accepted. It's something they've got to do and they're pretty proud of it. You recognise the old and more experienced guys when you first come in as a young player, but they welcome you."

There's work to be done at No 8, where Kieran Read sits well atop. Victor Vito is probably next in line. While Luke Romano is injured a gap behind Sam Whitelock and Brodie Retallick exists in the second-row. And despite Francis Saili's development, options in the midfield remain largely unproven.

Overall, though, the All Blacks' ability to seamlessly cover influential absences is the main reason they remain the envy of world rugby.