All Blacks spring surprise as McKenzie given pivotal role against Pumas

"Obviously stoked and probably didn't expect it," said the 28-year-old, who was not wanted by the All Blacks last year on his return from a season in Japan.

In 41 Tests, it will be only the third start in the 10 jersey for the Waikato Chiefs utility, and his first Test in 20 months.

Richie Mo'unga, who guided the Canterbury Crusaders to their victory over the Chiefs in the Super Rugby final two weeks ago, is on the bench, with Test centurion Beauden Barrett at fullback.

McKenzie said while he was first choice to pull the strings against Argentina in the opening Test of the year, he was taking nothing for granted.

"We've still got Richie and Baz (Barrett) playing good rugby, so I wouldn't say the jersey is mine whatsoever, but it is an opportunity," he said.

"For me, it's just about playing my game. Obviously, we've got a game plan but you just want to be yourself, be instinctive, and play the rugby that I tried to play all year."

Coach Ian Foster said the All Blacks' focus was "to build combinations in a vital year" with the World Cup just two months away.

"This is obviously a massive year, and we are really confident in the way that we've been building. We have had a short build-up but an effective one," he said, signalling defence as critical against Argentina.

"If you don't really commit in terms of your defensive line, then you struggle with them," he said.

"We know that they're really willing around the breakdown, and that's kind of where the battle often is against Argentina."

But Foster also appears to have one eye on the following week's encounter with South Africa in Auckland by resting veteran locks Sam Whitelock and Brodie Retallick and having Josh Lord in this third Test partnering Scott Barrett in the middle