But they are operating on thin resources right now, they have a relatively inexperienced captain, their bullish coach Darren Lehmann is stranded at home for health reasons, and in a crazy turnaround it is the Kiwis who have the scary fast bowlers.
Australian cricket teams don't lie down, but this might be shaping as the worst team they've sent here. Turn a few screws, and it could turn to disarray.
In contrast, McCullum's mob appears so high on confidence that they can charge into the cauldron even without leading lights Ross Taylor and Tim Southee.
The remaining one dayers on Saturday and Monday are important in themselves, but they are further chances to demoralise Australia before the test series.
Is this treading dangerously considering it's Australia we are talking about? Never. The demolition job at Eden Park is something to be wildly celebrated. We've had so many dark days against Australia that a win like that deserves fireworks.
And Steve Smith is facing a potential firestorm. New Zealand cricket teams can get away with sub-par performances, but the world caves in on Australian sides who don't live up to a glorious past.
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Smith's rise to the Aussie captaincy and status as one of the best batsmen in the game has been somewhat surprising. That tells a story, because he doesn't have a lot of experience to turn to, and certainly not in the class of previous Australian teams.
Now is the time for New Zealand to put a foot on the throat in the one dayers, and hopefully in front of packed houses at Wellington and Hamilton.
It feels as if New Zealand is consistently punching above its weight like never before, despite relative disappointments such as last year's tour of England. These players can write their names loud in history, by landing knockout blows in the test arena. Hopefully, Taylor will make it back from injury in time for that.
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