Openers Daniel Flynn and Martin Guptill negotiated 25 overs in the final session yesterday, if not without the occasional alarm.
Flynn, in his first test since the end of 2009, was struck by both Dale Steyn and Morne Morkel, and he was dropped, a difficult chance high to his right, by wicketkeeper Mark Boucher off Morkel on four.
But grit has long been rated one of his more visible traits, and so he survived, even taking the attack to the bowlers late on. He starts today on 35, with Guptill on 28.
It is by a distance New Zealand's best opening partnership of the series. That wouldn't be hard, considering the previous four efforts produced seven, 15, 11 and one.
New Zealand's ambitions of levelling the series effectively evaporated over the first two rain-hit days during which South Africa shut out a bowling attack big on determination but short on inspiration.
Business resumed as usual yesterday, with opener Petersen and JP Duminy, in his first test for two years, both hitting centuries.
Petersen, patience personified, went on to the highest of his three test centuries, 156, over eight hours of conscientious, unhurried work.
Duminy, more assertive and ambitious, made 103, at one point taking four boundaries in five Doug Bracewell deliveries. They added 200 which finally turned the lock on a door which had been shut the previous day.
The later batsmen rubbed it in on a comfortable strip, as if to say there would be no easing of the foot on New Zealand's throat.
New Zealand's bowlers finally had something to smile about in the middle session, largely through the efforts of lively Mark Gillespie. He was the driving force in a period when New Zealand took six for 112 in 34 overs.
Having been recalled after a three-year absence for the second test at Hamilton and responding with five for 59 in the South African first innings, Gillespie took six for 113 from 33.4 overs of hustle and perspiration.
It was a fitting reward for the stocky Wellington quick, whose Test record in a career of lengthy gaps is an impressive 22 wickets at 26.18 in 5 Tests since late 2007.
Guptill had his best score of the series by stumps; the nuggety Flynn pulled Philander for six in the course of taking 14 off the over, and looks ready for a fight.
First Gillespie, then Flynn, in an unfamiliar role, produced reason for some satisfaction in the New Zealand camp, and they haven't had much to smile about in the past two tests.