It was a must-win for the Northern Knights at Seddon Park while the bottom of the table Auckland Aces motored on down to Hamilton with nothing to lose but dignity in a star-studded neighbourhood derby.
Facing elimination if his side lost, home captain Anton Devcich won the toss, his Knights men fired up to deliver in a crunch game that was also Colin de Grandhomme's 200th T20 match.
Devcich sent in the Aces, and his team got off to a great start as BLACKCAPS took on BLACKCAPS head to head.
The hosts were quickly the ones smiling, two big names in Martin Guptill (mistiming Trent Boult on 2) and Glenn Phillips (bowled by Tim Southee straight after having belted him for his solitary boundary) gone inside the first 3.2 overs.
Sean Solia and Mark Chapman held on until the change bowlers came on - and then Chapman unleashed the first six of the innings, off Scott Kuggeleijn, as the visitors started to pull together some momentum.
Fourth change Anurag Verma soon had Solia nicking his third delivery behind to end the short stand, however dangerous Chapman quickly recombined with captain Robbie O'Donnell and, this time, got moving in partnership for the substantial contribution to the innings.
The pair put on 89 for the fourth, batting for just over 10 overs through the middle. Chapman dominated the strike whilst O'Donnell chimed in himself with sixes off Mitch Santner and Southee.
Showing how badly the Aces had missed him earlier in their campaign, Chapman blasted four sixes and six boundaries in his 51-ball 69 before Southee finally got him caught behind in the 16th, for Southee's second wicket.
It would be the last to fall in the innings as the Aces got through to 162 for four, helped by Ben Horne peeling a six off Boult's second to last ball of the last over.
Had they got enough? The jury was out, but the Aces' opening bowlers, spinner Louis Delport and the big paceman Kyle Jamieson, strung together enough early dot balls to put the Knights on notice that this was going to be anything but a doddle.
Tim Seifert had faced almost all the first three overs on his own, for a trio of boundaries when he got the opportunity. But when Ross ter Braak came on and, likewise, kept things tight once found his line, run pressure perhaps told as Seifert found himself walking back for a run-a-ball 13.
The Aces had meanwhile lost a valuable fielding asset in an injured Guptill, but sub fielder - and the assistant coach - Johnny Bassett-Graham showed he also had decent hands on him as he hauled in a tricky catch to remove Katene Clarke off Jamieson at 24/2.
That brought the big man de Grandhomme to the middle to join his BLACKCAPS skipper Kane Williamson, and soon the pair were peeling of 12- and 14-overs.
De Grandhomme had just smoked Danru Ferns for back to back sixes when he was caught just inside the rope by a delighted Chapman: third time unlucky, and another wicket just when the Knights didn't need it.
But the BLACKCAPS all-stars just kept on coming in the deep line-up, Santner then Kuggeleijn joining Williamson for cameos.
Although the required run rate was circling high, the master batsman remained at his post and, as long as he did, the Aces had reason to be concerned. When he was joined by Southee at 112/6 in the 15th, Williamson had just broken out the third of three sixes, calmly squeezing the accelerator as the pair began to take charge of the required rate.
The final over began with the Knights needing nine for the win - and little going right for the Aces in the field.
Ter Braak had impressed earlier with the ball, but he had a moment to forget as Jamieson rocketed the ball into him for what would have been a very useful runout in the last over, only for the bowler to fumble and drop the ball when six was needed from his four remaining deliveries.
It was a costly mistake. The very next ball Southee swung hard, and was lucky not to lose his stumps, but instead the ball streaked away behind him to the rope: the scores were now tied.
There was yet another twist in the tail of this thriller. Looking to go big off the next - the penultimate ball of the innings - Southee instead skied ter Braak's slower ball, and was caught.
Now the scores were still level with one ball to go, the Knights' life in the campaign depending on the last act of the game.
In strolled Verma to the non-strikers: the batsmen had crossed, putting King Kane on strike for the crucial ball. And of course Williamson just ate up the pressure and coolly smacked ter Braak for the winning boundary, finishing on a 55-ball 79 not out.
The Knights had lived to fight another day on the points table - but the nailbiter had also cost them a chance to seriously boost their net run rate. Their hopes remain hanging by a mathematical pink thread, fate effectively out of their hands despite a memorable win.