With a stiff neck from a training mishap ruling Barrett out of the Christchurch test, his Auckland Blues teammate Stephen Perofeta (25) will have his chance to debut off the bench.
Three years before Barrett crossed to the Blues from the Wellington Hurricanes in 2020, a 20-year-old Perofeta was the Super Rugby side's starting flyhalf when they upset the touring British and Irish Lions 22-16 at Eden Park.
The young playmaker seemed on a fast track to an All Blacks jersey but a string of injuries stalled his progress and Mo'unga emerged to become Barrett's chief rival at 10.
Barrett has had most of the position at the Blues, relegating Perofeta to fullback, but the pair's combination has underpinned the team's rise from habitual underachievers to championship contenders.
Perofeta could have few better mentors than twice world-player-of-the-year Barrett for the step up to test level as the All Blacks look for back-to-back wins after the breakthrough victory over South Africa at Ellis Park.
"I'm extremely grateful and blessed to be in this position, as unfortunate as it is for Baz (Barrett), and his injury, I would never want to wish that on anyone," Perofeta said of his call-up.
"Growing up as a kid, it's always a dream. But it has felt so far (away).
"Just coming from Whanganui - a small town - I thought it was never achievable. But through the support I've had, throughout my whole journey, the help I've got ... I'm bloody excited."
With Barrett expected to be fit for the second match against Argentina in Hamilton next week, Perofeta may only have a quick taste of test rugby.
Depending on the match situation, he could end up at fullback in place of Barrett's brother Jordie instead of the driver's seat if starting flyhalf Mo'unga is given an early rest by the All Blacks staff.
Perofeta's Blues teammate, the rugby league convert Roger Tuivasa-Sheck, was given about 10 minutes for his test debut in the series-deciding defeat to Ireland in Wellington last month.
Though through no fault of his own, Tuivasa-Sheck has not been near an All Blacks jersey since and may have to wait a long time for another look-in.
All Blacks coach Ian Foster urged Perofeta to take his chance with both hands.
"He has been quite impressive behind the scenes," Foster said.
"And the opportunity has come... The whole group is excited about that. Got a lot of faith in him."
