'We just felt Saturday's the right time to try that particular part of the plan'

Steve Hansen believes the time is right to field gifted playmaker Beauden Barrett at fullback and won't rule out other profound positional changes to the All Blacks in World Cup year.

Hansen has potentially played his trump card two months out from the tournament in Japan by shifting five-eighth Barrett back to the open spaces for Saturday's Test against the Springboks in Wellington.

It will be the 28-year-old's first start at fullback in six years and creates an altered dimension to New Zealand's attacking makeup, with Richie Mo'unga bringing a more classical style to the No.10 jersey.

Hansen has retained just three starting players from the team who opened the Rugby Championship with a nervous 20-16 win over Argentina in Buenos Aires.

One of them is Barrett and another Ben Smith, who moves from fullback to wing. Lock Brodie Retallick is the lone forward retained.

Mo'unga faces his biggest assignment, having started just two of nine Tests in his rookie international season last year but his sheer weight of form for the Super Rugby champion Crusaders has almost forced Hansen's hand.

Critics have long said the free-running Barrett is an inferior game manager to Mo'unga and should return to fullback, where he shone as a junior and in his early All Blacks years off the bench.

Hansen believed two-time world player-of-the-year Barrett can shine there again in a move he has long considered.

"It's probably time. We've got a plan with a whole lot of things that we want to do before we get to the nitty gritty business (World Cup) and we just felt Saturday's the right time to try that particular part of the plan," he said.

"Obviously to replace Beauden at first five you've got to have someone that's pretty good.

"Richie's been playing very well for the last couple of years ... you've got two ball players on the park and you've got two world class players."

Hansen was guarded when asked if he may consider another momentous World Cup change by fielding veteran captain Kieran Read at blindside flanker, rather than the No.8 jersey he has owned for a decade.

Speculation around such a shift has mounted following the monstrous 2019 form of No.8 candidate Ardie Savea and a lack of blindside options.

"You'll have to wait and see. There's no point in me telling the world what we're doing," Hansen said.

"They can find out. It's a good question but I can't answer it."

Read is the only proven force in this weekend's experimental loose forward mix, with gun flankers Sam Cane and Savea omitted.

Matt Todd and Shannon Frizell get rare starts on the side of the scrum while Dalton Papali'i and Vaea Fifita are bench options.

- AAP