"He gives a little bit of variation. 'Batesy' has played well for Auckland for a number of years and I'm sure he'll do well," McCullum said.
The two tours have been dovetailed, so the South African trip begins with T20s and ODIs before ending with three tests. New Zealand will have 11 short-form games in a row, with the tours bookended by five-day cricket.
The schedule minimises the swapping from one form to another.
One player whose chances of facing South Africa may become clearer today is Canterbury batsman Dean Brownlie. Having damaged a finger at Whangarei on Monday, the initial prognosis of a sore finger turned into a fracture on Tuesday. When he might return is expected to be known today after further assessment in Christchurch from an orthopaedic surgeon.
For the moment, McCullum is stressing the old line about not looking beyond the business at hand.
"We've got to make sure we're efficient in what we do. Zimbabwe have shown if we take our eye off the ball they can certainly come back and take the game to you."
This is a constant line New Zealand are happy to run out. After all, they did win the final ODI in Bulawayo last October and pushed New Zealand in their only test at the same ground shortly after. But that was home soil, different playing conditions.
You want Zimbabwe to do well today, for a range of reasons. But short of finding a telephone box and red and blue cape lying about, Zimbabwe are unlikely to put up more than moderate resistance.
They are well off the pace, and that's not their fault. It's more the circumstances of having so few opportunities overseas, therefore unfamiliarity with the conditions, and a New Zealand side playing strongly and with confidence.
So have New Zealand been left underdone for South Africa the way the Zimbabwe visit has gone?
That won't become apparent until the next series begins. But New Zealand do have a bit of momentum, players in decent form and with a run of Ws with which to feel good about themselves.
TODAY'S ACTION
New Zealand v Zimbabwe
McLean Park, Napier, 2pm.
New Zealand: (from) Brendon McCullum (c), Martin Guptill, Rob Nicol, Kane Williamson, Tom Latham, Nathan McCullum, Andrew Ellis, Jacob Oram, Doug Bracewell, Kyle Mills, Tarun Nethula, Tim Southee, Michael Bates.
Zimbabwe: (from) Brendan Taylor (c), Hamilton Masakadza, Stuart Matsikenyeri, Tino Mawoyo, Regis Chakabva, Tatenda Taibu, Malcolm Waller, Forster Mutizwa, Elton Chigumbura, Shingi Masakadza, Ray Price, Keegan Meth, Prosper Utseya, Kyle Jarvis, Brian Vitori.