All Blacks v Argentina: Ian Foster on Beauden Barrett injury and rookie Stephen Perofeta's big chance

All Blacks coach Ian Foster has moved to allay fears that Beauden Barrett could be set for another lengthy stint on the sideline after sustaining a knock at training on Tuesday.

Barrett has been ruled out of this weekend's test against the Pumas in Christchurch after injuring his neck during a routine cleanout drill.

Three weeks ago Barrett suffered a nasty fall onto his neck from a great height while attempting to catch a high ball in the first test loss to the Springboks in South Africa - yet Foster is unflustered by the nature of the latest injury.

"Not really," Foster said after maintaining the same starting team and injecting Stephen Perofeta in place of Barrett on the bench for his test debut. "It's based on the injury and data we got from the medical staff that it's going to take a little while to free up.

"He took a knock in the neck during a cleanout drill and it's quite stiff. It's not too bad though. There's no HIA issues but there's enough there to stop him being free so we made an early call."

Beauden Barrett has been ruled out of this weekend's test against the Pumas with a neck injury. Photo / Photosport

At this point, Foster suggested Barrett could recover in time for next week's return test against the Pumas in Hamilton.

"It's day-by-day at the moment. I haven't heard anything to say he's not going to be available next week but we'll see what unfolds."

All Blacks and Crusaders lock Scott Barrett reflected his brother's disappointment at the timing of the blow.

"He's doing alright," Barrett said. "It's frustrating when you get ruled out during a training session during the week. We're feeling for him but Stevie will step in and do a superb job."

Barrett's absence paves the way for Richie Mo'unga to retain the starting first five-eighth duties on his home patch after delivering an influential performance in the inspired Ellis Park victory. Mo'unga's early territorial control, his depth and width of passing, helped spark the All Blacks upset triumph on the back of a vastly improved forward platform.

Seven years after debuting for Whanganui against Horowhenua Kapiti, six years after progressing to first represent Taranaki, classy Blues playmaker Perofeta is now in line to savour his test debut.

Stephen Perofeta is set to make his All Blacks debut against the Pumas. Photo / Photosport

When he takes the Orangetheory Stadium field at first-five or fullback the 25-year-old will become the first All Black who started his career in the Heartland Championship since Mid Canterbury prop Tim Perry.

Foster indicated Perofeta's test debut was originally planned for next week. Barrett's injury has instead fast-tracked his promotion after assuming a watching brief for this year's first five tests against Ireland and South Africa.

"He's been quite impressive behind the scenes," Foster said. "The opportunity has come – there was potential for it to be next week but it's this week and the whole group is excited by that. We've got a lot of faith in him.

"He's confident, he's happy to talk in front of the group but the main thing is he's learning on the park. He's had a role to fill at 15 and 10 so there's a lot to learn but he's done that particularly well."