Why 20-year-old Tupou Vaa'i has won the right to start in the All Blacks second row ahead of fit again Scott Barrett

Ian Foster has revealed that returning lock Scott Barrett could well have suited up for the All Blacks in their opening test of the year, if he'd been needed.

In the first game of the Bledisloe Cup series, Sam Whitelock and Patrick Tuipulotu combined to form a secure second row. 20-year-old Tupou Vaa'i earned his first test cap off the bench, entering the field late in the game.

Barrett, who was absent for the Crusaders' successful Super Rugby Aotearoa campaign, has only recently returned to full training since recovering from foot surgery.

Following today's team naming, which saw Vaa'i elevated to start alongside Tuipulotu due to an injury to Sam Whitelock, and Barrett named on the bench, Foster revealed that Barrett could have played in last weekend's match.

Instead of throwing the 26-year-old straight back into the fold, however, Foster elected to hand the bench spot to Vaa'i. It's a similar story this week, with Vaa'i earning his maiden start.

"[Barrett's] been out for a while and in this particular case, it's a vote of confidence in Tupou, who should be proud of his efforts last week off the bench," Foster said.

Vaa'i joined the fray in the 76th minute - which, under normal circumstances, see a player earn just a handful of token minutes. Of course, the game instead continued for a further eight minutes after the hooter and Vaa'i had plenty of time to acquaint himself to test rugby.

The Chiefs lock even managed some cheeky disruption in a Wallabies' ruck late in the game which, had it been spied by the referees, could have spelled victory for Australia.

Foster and his fellow selectors were impressed with what 20-year-old Tupou added from the pine and his starting spot this week is just desserts for his composed display.

“It’s a great opportunity for Tupou," Foster said. "We enjoyed seeing him come off the bench last weekend, he brought a lot of energy and he has settled in well."

Following the team announcement, Patrick Tuipulotu, who will be the senior lock on Sunday, was adamant that he won't need to provide Vaa'i with too much support during the match.

"He's here for a reason and I don't need to do much," Tuipulotu said. "I just need to do my role and that will make his easier. We're locking together and that's exciting. He'll bring energy."

Certainly, Vaa'i won't need any motivation. The Wesley College alumnus didn't even have a Super Rugby contract at the start of the year but is now set to start in a Bledisloe Cup match.

"My excitement levels are really high," Vaa'i said of his elevation to the starting team. "I'm trying to focus on my role leading into training this afternoon."

Speaking to The XV following his initial selection in the All Blacks, Vaa'i revealed how excited he was to play alongside Tuipulotu in the North v South match earlier this year.

“Patty was a guy I tried to model my game around, I always looked up to him during my First XV years at school,” he said.

"It was a special moment for me, to be finally playing with Patrick Tuipulotu, a guy I’d always looked up to, and to see him lead the team the way he did. I was stoked to be able to rub shoulders with him and to lock down with him in the pack and in the scrum."

No doubt, this weekend's test match will be another massive moment for Vaa'i - and the young lock expects he'll have a few supporters at Eden Park on Sunday.

"I told my family. Pretty sure the whole of South Auckland is going to be coming," he joked.