Shreyas Iyer has threatened to play an innings like this for India for a long time; an innings where he seemed invincible.

He had no business being that. He should have been very vincible. Out of place even. He had never played a T20I away from home before, let alone dealt with one where he was the last man standing against an opposition transformed.

One of the first things he was subjected to after he walked out to bat in Auckland was the sight of his captain being dismissed. New Zealand claimed the wicket of Virat Kohli through a breathtaking catch in the outfield. Stuff like that can completely change the mindset of the fielding team.

It gives them belief, the single most important thing when the pressure is on.

But Iyer wouldn't back down. Actually, he kept stepping the bad word up.

Two balls after the Kohli dismissal, he backed away and sent a perfectly good length ball aimed at his stumps to the long-off boundary.

It was just the perfect response because Eden Park is a place where boundaries are the only things that matter. Bowling teams go there trying to prevent them at all cost and batting teams play without any inhibition because they know even mishits can result in six runs.

New Zealand had already benefited from such an approach, with even Kane Williamson happy to slog it around. He reached his fifty off 25 balls, quicker than Colin Munro, the designated dasher of the line-up. If a batsman whose best feature is how late he plays a cricket ball is happy to go out in search for it and manufacture shots that aren't on, then he is doing it because he has no choice.

Iyer knew this well. And even before he touched down in New Zealand, he had been advised to break the shackles.

India were in the middle of a series decider against Australia this past week when he had walked out to bat. Most of the work had already been done in that game, but it still ain't fun when Pat Cummins and Mitchell Starc are charging in straight at you.

"I knew they were going to attack me on my body," Iyer said. "They were trying to get on my head."

Kohli was at the other end in Bengaluru. "Shreyas came up and asked me, 'Should I attack?' I said yes because the pressure was off us. Because of the [good] position [we were in], I wanted it to be a part of his learning, to take on their best bowlers and his execution was outstanding."

Iyer actually went one better here. True, New Zealand did not have the same quality of bowlers, but they are among the very best in making the most of scoreboard pressure. The World Cup pretty much proved that and they were in the middle of an encore.

India spent a period where they made only 22 runs in three overs. It was during this period that they lost both KL Rahul (56 off 27) and Kohli (45 off 32). The equation now read 75 off 48 balls - exactly the kind of situation that has got the better of this side. There was too much of the game still left and none of the top three were around to deal with it.

There was a moment - a fleeting moment - when Iyer seemed affected by this. In the 16th over, he went really hard at a legbreak and lost all of his shape, but he had kept enough of his balance to avoid being stumped. Whatever happened between that ball and the next is where India won this game.

Maybe Iyer slowed himself down. Maybe he closed his eyes, took in a breath, blocked out the noise and listened only to that voice in his head. Maybe it told him to calm down.

The next ball from Sodhi was a tease. The kind Yuzvendra Chahal dishes out all the time. The wide legbreak. The one that a batsman panicking because of the required rate would try to slog into the leg side. Iyer hit that to the point boundary. He stood tall. He moved towards the ball - who does that in T20 cricket? - got his head on top of it and cut it well to the left of the fielder in the deep. It was beautiful.

From there on, Iyer would not be stopped. He would even go on to make his opponents look utterly silly. To be fair, Eden Park has a hand in that as well.

The only way anyone can keep the runs down there is by either targeting the body and by using slower balls. Tim Southee had already indulged in his variation at the start of the 17th over. Iyer knew the next one would be at his body. So as it was being sent down, he stepped across his stumps and suddenly the short ball meant to cramp him was, in effect, a short ball down the leg side. An expertly timed pull shot later, India had six more.

Iyer was hyper aware of both his game and what the New Zealand bowlers were trying to do. In the next over, when Hamish Bennett started around the wicket, he knew the ball would be on leg stump. He knew that with a tiny step to his right he would have access to the long leg boundary again. That clever little leg glance was followed by an entirely orthodox flick past long-on.

Iyer paced this chase in a manner that was truly incredible. Five of his eight boundaries came off either the first or the second ball of the over. He knew he had to find them otherwise he would never be able to put the pressure back on New Zealand; to make them doubt themselves even though they had the upper hand having dismissed India's top three. And that is the biggest takeaway from this game. As big as the win itself.

India finally have a No. 4 again.

Alagappan Muthu is a sub-editor at ESPNcricinfo