The chatter about is that they may look to play three specialist spinners: Mitchell Santner, Ish Sodhi and the recalled veteran Jeetan Patel. Legspinner Sodhi was good value in both games one and two, including the previous Seddon Park match.
Patel's offspin brings him into play against South Africa's three lefthanders in their anticipated top six. Santner is a certainty.
But doing that leaves a major question over balance. Trent Boult and Tim Southee must play, meaning the bowlers start from No 7 in the batting order. Wicketkeeper Luke Ronchi is expected to get his chance today and must bat in the top six; under that scenario only one of the in-form Jimmy Neesham and Colin de Grandhomme can be fitted in.
The counter argument would run as it does when the question of playing a fourth seamer is raised: can three spinners automatically do a better job than two?
At the other end of the batting order Martin Guptill makes a welcome return after getting over a hamstring injury.
He was last seen against Australia at Eden Park on January 30. Hamstring injuries counted him out of the three-game Bangladesh T20 series, and now he's missed four ODIs against Australia and South Africa.
"It's been a bit frustrating, but I'm looking forward to getting amongst it," Guptill said yesterday. He has been hitting a few balls but most of his focus recently has been on rehab work to get his hamstrings right.
"My role in the side doesn't change. It does feel a while since I've been with the team, but hopefully I can fit straight back in and nothing changes."
South Africa won't change either, he reckons. "They never let the foot off the throat and we have to match them blow for blow. It's going to be a tough couple of games."
South Africa's captain, AB de Villiers, believes he's picked up some of the captaincy foresight of Brendon McCullum. He said his captaincy, rather than his batting, was giving him the most pleasure. So far de Villiers has been out twice in scoring 167 off 163 balls in the three matches.
"I just love to contribute and to see the joy in my teammates' faces after I've done something good," he said. "I'm enjoying it now more than ever. I feel I have a good understanding of the game, a good gut feel of what's coming and what's going to happen.
"A guy like McCullum does that really well, he sees what's going to happen in 10 overs' time. That's important for a captain."
Today's contest should be a cracker. South Africa would rather wrap the rubber up than leave it till the last chance next Saturday at Eden Park. New Zealand will be desperate to take the series to the finishing line. Talk about all to play for.
NZ v South Africa
• Fourth ODI, Seddon Park, 2pm today
• New Zealand: (from) Kane Williamson (c), Martin Guptill, Dean Brownlie, Tom Latham, Ross Taylor, Neil Broom, Luke Ronchi, Jimmy Neesham, Colin de Grandhomme, Mitch Santner, Ish Sodhi, Tim Southee, Lockie Ferguson, Jeetan Patel, Trent Boult.
• South Africa: (from) AB de Villiers (c), Quinton de Kock, Hashim Amla, Faf du Plessis, JP Duminy, David Miller, Farhaan Behardien, Dwaine Pretorius, Chris Morris, Wayne Parnell, Andile Phehlukwayo, Kagiso Rabada, Dane Paterson, Tabraiz Shamsi, Imran Tahir.
