In his next over, Santner pushed a ball up outside off to lure Shadab into driving over cover. The ball spun away from the right-hander but he had over-committed, and ballooned a catch to Henry Nicholls at backward point. Shadab departed for 54 off 77 balls.
The 38th and 40th overs conceded three runs and Pakistan were reeling again at 171 for seven.
The 25-year-old left-arm orthodox also picked up Faheem Ashraf for 23 off 15 balls in the 44th over, defusing another threat.
Santner's opening spell of none for 24 from six overs was tidy, but his second stint of three wickets for 16 from four overs underlined his value under pressure.
"On a holding wicket [at the Basin Reserve] there was more chance for me to get wickets," Santner said.
"Pakistan are good players on slower surfaces, but we took early poles in most games and they didn't have a platform to build from."
Part of Santner's bowling development has come with him mastering a carrom ball. The name comes from a subcontinental board game where discs are flicked into pockets, like snooker using your fingers.
In cricket, that means flicking a ball out of the hand using the middle finger and thumb.
The practice is decades-old as a means for finger spinners to turn the ball in the opposite direction. Indian spinner Ravichandran Ashwin has returned it to the mainstream.
Santner used the technique to bowl Pakistan opener Fakhar Zaman in the fourth ODI at Hamilton. The delivery reappeared in Wellington.
"I've been trying it in the nets with a similar grip to Ashwin. He used it against us in the [2016] test series. I thought 'that's not a bad ball' so I gave it a crack.
"I used it in T20 county cricket on wickets that suited, but it's hard to generate a lot of revs, because you're just flicking it out.
"I might have to disguise it more because every time I look up it's on the big screen. It adds another element to my game. If I can get one to go the other way, it puts doubt in a batsman's mind."
The next question is whether Santner gets to showcase such abilities in the Indian Premier League. The auction is next weekend.
His bowling is respected on the subcontinent – Indian captain Virat Kohli is understood to rate him highly – but that has yet to be recognised with an IPL contract, given the plethora of local tweakers.
In 2016 Santner's stocks appeared to rise at the World T20 in India, after joining Ish Sodhi and England's David Willey in taking the most wickets during the competition proper. His 10 came at an average of 11.40, strike rate of 12 and economy rate of 6.27. His best bowling – 4-11 in New Zealand's win against India - shocked the tournament as he dismissed T20 gurus MS Dhoni, Rohit Sharma and Suresh Raina.
Martin Guptill probably summed up Santner's bowling progress best at the post-match press conference.
"He bowled exceptionally well through the whole series. He has great control over what he's doing and is turning himself into world class spinner."
Whether the IPL owners see it that way remains to be seen.
