The Silver Ferns took a 2-1 series lead by holding their nerve in a typically tense finale in Sunday's third Test, while the Diamonds could only manage one goal in the frantic final four minutes at Qudos Bank Arena in Sydney.

Ameliaranne Ekenasio (27/29) scored what proved to be the winner with barely 20 seconds left on the clock, with the Diamonds' last attacking assault chopped off by Langman to secure New Zealand's first triumph on Australian soil since 2016.

It means the Silver Ferns can win the Constellation Cup for just the second time if they prevail in Perth on Sunday, in what would be another statement of supremacy to back up July's World Cup final win over Australia.

"It would be massive," said Langman, who was crowned MVP of the match. "It's an opportunity for us, especially after the World Cup. We really do want to send this new-age Ferns [team] into the future and have a little bit of dominance on our side."

The Diamonds have won the trophy eight times in the nine years it has been contested, including the last six in a row, and can still win this year's edition on goal difference if they beat New Zealand in Perth.

But coach Lisa Alexander said she felt tactically hobbled by the absence of gun midcourter Paige Hadley, who will miss the remainder of the series due to a fractured wrist sustained in Wednesday's game two in Auckland, and watched on from the sidelines along with the biggest netball crowd anywhere in the world this year.

"I see that very starkly now," Alexander said. "That's what's disappointing because I couldn't make the changes I probably would have liked to have made just to freshen up the centre court a bit more."

Alexander also conceded her decision to withdraw the electric Gretel Tippett (13/13) for Tegan Philip in the second quarter "didn't quite work" and suggested further changes might be necessary at the defensive end to quell the influence of New Zealand's star shooters Ekenasio and Maria Folau (27/31), both of whom regularly drained shots from distance.

Sarah Klau was sent on at goalkeeper midway through the third term to keep Folau on a leash and Alexander hinted she could be playing with her NSW Swifts teammate Maddy Turner next week.

"I've got some plans for that. We've got the two Swifts players who play a really good split circle and we might need to trial that. We need to see how that works," she said.

Caitlin Thwaites (16/17) led the way for the Diamonds after replacing captain and starting goal shooter Caitlin Bassett (19/21), who conceded she was too "static" with her movement at times, while Laura Scherian was a constant creative force with 24 assists.

Australia made a blistering start, passing the ball with incredible speed and precision to open up an early six-goal lead, but their momentum did not last for long enough and they squandered their opportunities to skip further ahead in the first and second quarters.

"We need to really lock down and make sure we bring that [more consistently] on Sunday but of course our opponent doesn't always allow us to do that," Alexander said.

Silver Ferns coach Noeline Taurua said it came down to "sheer determination and grit" in the dying moments.

"When things needed to happen, we were able to do it," she said. "[But] there's not much between one point. I'm really glad we're on the right side of the ledger."

NEW ZEALAND 54 (Ameliaranne Ekenasio 27 Maria Folau 27) bt AUSTRALIA 53 (Caitlin Bassett 19 Caitlin Thwaites 16 Gretel Tippett 13 Tegan Philip 5) at Qudos Bank Arena.