"The fracture is a little worse than first thought, ruling him out for at least two weeks," coach Mike Hesson said. "Hopefully it [the operation] makes him available for World T20 selection."
Tom Latham was originally listed for the first two ODIs against Pakistan, raising the prospect he might be released to play for Canterbury in the Ford Trophy final against Central Districts on Saturday. He will stay with the New Zealand squad as cover for McCullum, just in case.
"Hopefully Brendon will be right, but it's important that we don't expose ourselves. We need the right players," Hesson said.
As forecast, Luke Ronchi will return as wicketkeeper for the Chappell-Hadlee series after a week's break.
The McLean Park ground required five inspections by umpires Bruce Oxenford and Brent Bowden before a final decision was made just after 6.20pm.
Earlier, when the covers were removed, all-rounder Grant Elliott simultaneously splashed in the infield.
It was felt player safety would have been compromised in the soggy conditions.
There were a few obligatory boos, a handshake between captains Kane Williamson and Azhar Ali, then the crowd shuffled out the gates with the option to get autographs.
A local proverb suggested if you want to break a drought in Hawkes Bay, schedule a cricket match. So it proved.
The rain stopped mid-afternoon and an estimated 300 fans camped in the main stand until the final pronouncement, many with cartons of hot chips for company. A cut-off time of 7.17pm was set as the latest for play to start.
The umpires emerged, obscured by umbrellas, at 3.30pm for a second inspection. One dug a heel into the wicket block like Don Clarke preparing a 1960s place kick. He would be wishing he had worn gumboots.
The tractor and super sopper initially heading to the middle gave the impression of driving through a wave at the beach.
"The umpires have to make every effort," Hesson said. "And [groundsman] Phil [Stoyanoff] and his team did the same. It's a shame for the bay, we would've had a good crowd today, but you've got to take the emotion out of it."
NZC's head of cricket, Lindsay Crocker, said a reserve day was not feasible.
"Logistics is a boring word but also the fundamental reason why we don't do it [reserve days].
"Delaying would mean ensuring we had flights and hotels available. We'd then have to double book everywhere and costs would go through the roof when you consider it involves two touring squads, match officials, the event team, broadcasting crews and media. That's probably 100-150 people or more.
"Having it a dollar each way is not that easy."
