Among the theories which do the rounds about the Newlands ground in Cape Town - and McCullum should be ready as New Zealand captains have won three of the four tosses at Newlands between the teams - is that if the skies are overcast and a breeze is up, there is good reason to ponder bowling first. Otherwise, get the opening batsmen into business from the off.
"While it may be tough early on you want to be batting in front of the game," McCullum said. "That's something we want to try and look at from this youngish batting line-up, that they play their cricket from the front."
Bowling coach Shane Bond had a neat line on deciding what to do. There is a brewery next to the ground.
"They always say if you can smell the hops it will swing. If not, it'll be flat," he said.
Whatever happens with the coin, there's no question New Zealand, serious underdogs as the respective world rankings of No1 and No8 indicate, must get out of the blocks smartly tonight.
They were still keeping mum yesterday on their choice of third seamer to work alongside Trent Boult and Doug Bracewell. Chris Martin, New Zealand's third-highest wicket taker, has the experience and will likely get the nod ahead of left armer Neil Wagner.
Dean Brownlie has recovered from a stomach bug and his ability against fast bowling, having been raised on the bouncy strips of Perth, could be important.
McCullum is hoping for early momentum against a South African side that has not played a test for a month and - here the optimism kicks in - might take some time to find their range again.
"I anticipate we'll compete well and hopefully stand up in the big moments, put them under some pressure and see what happens," he said.
South Africa should have the world's best allrounder, Jacques Kallis, restored to full health after a break for a hamstring strain.
He needs just 20 runs to join Sachin Tendulkar, Ricky Ponting and Rahul Dravid as the only batsman with more than 13,000 test runs.
However, top-class seamer Vernon Philander was last night rated unlikely to be fit after a hamstring injury. Rory Kleinveldt, a fast-medium bowler, will take his place.
But there are threats for New Zealand to consider all across the park.
There are no better seamers than Dale Steyn and Morne Morkel, while the batting lineup dominates the world rankings.
"I'm looking forward to it," the combative McCullum said. "Obviously we've had a reasonably tough time in the last little while, but we've got a squad here which can compete."
New Zealand have faced plenty of stiff assignments in their test history. But given the fraught backdrop, including the ill-handled change of captaincy, loss of important players like Dan Vettori and Tim Southee to injury, and quality of the opposition, few leap to mind as readily as this.
South Africa v NZ
Newlands, 9.30 tonight
South Africa: (from) Graeme Smith (c), Alviro Petersen, Hashim Amla, Jacques Kallis, AB de Villiers, Faf du Plessis, Dean Elgar, Jacques Rudolph, Robin Peterson, Dale Steyn, Morne Morkel, Vernon Philander, Rory Kleinveldt.
New Zealand: (probable) Brendon McCullum (c), Martin Guptill, Kane Williamson, Dean Brownlie, Daniel Flynn, BJ Watling, James Franklin, Doug Bracewell, Jeetan Patel, Trent Boult, Chris Martin or Neil Wagner.
