The 25-year-old's performances this year have gone a long way to settling the debate over who should succeed world leading points scorer Dan Carter.
Barrett, who had mostly been used as a super sub by All Blacks coach Steve Hansen, started the third test against Wales in June and then ensured Aaron Cruden would not return to the All Blacks role by guiding the Wellington Hurricanes to their first Super Rugby title.
"He has got an opportunity and he's played out of his skin, to the point where you can't not pick him," Hansen said of the decision to give Barrett the role against the Wallabies and Pumas, who they meet in Hamilton on Saturday.
Barrett's searing pace had always set him apart from most other flyhalves, but Hansen added that the way he had guided the Hurricanes in atrocious weather conditions throughout the July Super Rugby playoffs had taken his game to a new level.
"He has been exposed to that pressure and having to drive his team around the park," Hansen said.
"If you think back to the weather conditions, they weren't the best and he really had to step up and own that and he did that well and has taken some real confidence out of that.
"That has allowed him to take his game to another level."
Such was the way Barrett controlled the Hurricanes field position and the tempo of their game, media in the rugby-mad country have even suggested he could eventually surpass the impact made by the three-times World Player of the Year Carter.
That form ensured Barrett, who earned his first test start at flyhalf against Argentina two years ago in Napier, was retained as flyhalf against the Wallabies in their first two Rugby Championship clashes, where he was again singled out for praise.
The Pumas, however, will provide a different challenge for Barrett in Hamilton, where he will probably need to create more from less.
Agustin Creevy's team are likely to be more combative and physical in the contact areas than an underperforming Wallabies side, while their strong pack should provide a more stable set piece.
While Hansen has also been complimentary of Barrett's form, and placed faith in him, he also sent a tacit warning about New Zealand's player depth.
"If he sits on his laurels and gets complacent then people will go past him," Hansen said.
"(But) I'm sure he'll get better, he's got a desire to want to get better."
(Editing by Peter Rutherford)
