According to the stuff.co.nz website, with Trent Boult and probably Doug Bracewell assured of spots in the injured Tim Southee's absence, it will leave either veteran Chris Martin or left-armer Neil Wagner as the unlucky one when the coin flips at Newlands.
Martin is expected to have the inside running, meaning Wagner, spinner Bruce Martin and late callups Mitchell McClenaghan and Colin Munro would be the ones to miss out from the 15-man squad.
"There's probably still one contentious spot and we need to make sure we do a pretty good assessment of the wicket then finalise that last place. The balance is reasonably set, we've got to make sure we select that person for the last (bowling) role," McCullum said after today's drawn warmup match in Paarl.
The top-seven is carved in stone, with McCullum partnering Martin Guptill at the top, followed by Kane Williamson, Dean Brownlie, Daniel Flynn, wicketkeeper BJ Watling and all-rounder James Franklin. Jeetan Patel looks likely to be the solitary spinner.
Watling will keep wicket for the first time since the Zimbabwe Test in January, after which he suffered an injury which handed Kruger van Wyk his chance.
McCullum also put to bed rumours he may reclaim the gloves and drop down the order.
"Absolutely not. That career has passed me, unfortunately, so it's BJ's opportunity and he kept really well in the warmup game on a tough surface. He's earned his chance, he banged down the door with his performances in the shorter version and he was the incumbent prior to his injury."
Recalled opener Peter Fulton's tour-ending knee injury ensured McCullum would remain at the top of the order against the might of South African quicks Dale Steyn and Morne Morkel.
"I'll open the batting and Dean will come in at four and we'll keep Daniel Flynn at five. That's a pretty good top five and hopefully we can find some ways to put some partnerships together and put some pressure back on South Africa."
Brownlie scored just six on Sunday after being laid low by a stomach
bug, but he'd spent time in the field and in the nets and was declared
100 percent fit for his Test recall.
McCullum said the docile Paarl pitch was completely different to the expected bouncy surface at Newlands.
After trailing by 48 on the first innings against a South African Invitation XI, New Zealand were 117-2 when stumps were pulled early, with Guptill 68 not out. The three days still served a purpose, McCullum said, as others got through some solid net sessions.
"The bowlers got through some tough toil and ticked off some bowling loads and bowled reasonably well at times and most of the batters faced in excess of 60-70 balls so it was as good as we could hope for."