There is a fairly trite marketing campaign around this World T20 centred on a hashtag: #OneBigOver.

For a start, that seems a reductive way of advertising the most reduced format of the game - although the marketing guys might say the pulling power of your product is only as strong as the person in the crowd with the shortest attention span - but it also glosses the infinitesimal shifts in balance that make this format so engrossing.

What's more, it dismisses the high wire skills executed under extreme pressure by the players throughout a match, knowing that an error at the finest margin can shift the grains of sand each team stands upon.

The big over, in the sense of ransacking runs, was New Zealand's, coming when Ross Taylor lock, stock and barrelled Morne Morkel for three consecutive sixes that seemed to strike South Africa visibly in the gut. Morkel bowled several big overs, conceding 50 from 3, but it was one little over from Dale Steyn that throttled New Zealand, with seven required from six balls, and allowed South Africa to breathe the rarefied air that so often eludes them with the winning post in sight.

Ever since Michael Hussey led Australia past Pakistan in the semi-final of the 2010 World T20 with a display of finishing so brutal it should have earned him the nickname Mr Mortal Kombat, there has been a sense that the chasing side is never really out of the game unless they are flat out and asking for the mercy stroke.

Hussey only had three wickets to play with when Steve Smith got out at the start of the 18th over four years ago and Australia needed 48 from 17 balls. They won with a delivery to spare, thanks to one of the greatest innings the T20 format has seen. Yet bowlers have become finishers now, too.

Taylor's cool hitting and hard running looked to have pushed New Zealand into the box seat and the loss of Kane Williamson - after a half-century that hinted his subtler skills have a place in the most frenetic format - seemingly opened the way for the likes of Colin Munro, Corey Anderson and Luke Ronchi to complete the knockout. It was Steyn that got Williamson, though, Steyn whose two overs had cost only five runs, and Steyn who would return with great vengeance and furious anger on his mind.

With three overs to go, New Zealand were 142 for 4, requiring 29 to win; comfortably within the borders of Hussey country. But teams have worked on their strategies in these deathly moments, knowing pressure can have a cascading effect. On Monday in Mirpur, Australia were 161 for 5, requiring 31, at the start of the 18th over against Pakistan. They didn't make it. The day before, South Africa were closed out by Sri Lanka when they needed 29 from three themselves. Ten an over only requires a couple of well-timed shots. But wickets quickly change that.

What Lasith Malinga (or the threat of Lasith Malinga, for it was actually Nuwan Kulasekara's over that broke South Africa) and Saeed Ajmal did in those two games, Steyn did to New Zealand. His last two overs cost 12 runs and four wickets fell, wrenching a victory for South Africa that was one of the most breathtaking in this competition's brief history.

"He proved today why he's been the world's best bowler for such a long period of time, it was a fantastic bowling performance," South Africa's captain, Faf du Plessis, said. "As a captain to have a guy like that in the team, anything is possible. I thought New Zealand got themselves in the position where they should have won the game and something special was going to be required for us to take it away from them and Dale did just that.

"I said anything under eight required would be tough but I backed Dale to do it. We got it down to seven, which was a little bit less than I would have liked it but when you start with three dot balls then you feel like you're right back in it."

In a sense, Steyn's was one big over too. A huge over, in which he conceded only one scoring shot. But everything else had led up to that. The sands shifted as JP Duminy pulled South Africa from 42 for 3 to what turned out to be a defendable total with an innings of class and invention; and New Zealand conceded 70 off the last five overs, the excellence of their fielding undone by fractional bowling errors at the end.

Was Imran Tahir's dismissal of Brendon McCullum the key moment? Quinton de Kock's failure to do anything more than get a fingertip to a rasping top-edge from Anderson in Steyn's penultimate over seemed to bear the mark of significance. Perhaps Nathan McCullum's two senseless, futile swipes at Steyn, as Taylor stood becalmed and impotent at the other end, were the most crucial of them all. Maybe people will remember this game in terms of one big over but it was standing on the shoulders of giants.