Had it not been for Nicholls - who arrived with New Zealand in a pickle inside the first hour -- this would have been a sorry day for New Zealand.
''I think we're in a good spot. It's nice to removed both their openers so we're very happy to take those wickets. It'll be a big first hour tomorrow," Nicholls said tonight.
There was a bit for everyone yesterday - some top class seam bowling in favourable conditions from South Africa, gritty batting, poor dismissals, and a bizarre one, and a depressing slump after Nicholls had been removed, when New Zealand lost three for five in 24 balls.
Six wickets fell to the spinners, a feat last seen on day one at the Basin Reserve in 1946 when Australian legend Bill O'Reilly was making chopped liver out of New Zealand.
Nicholls had four test fifties before today, which was his 19th innings. He could have got his first century against Bangladesh in Christchurch in January but squandered it at 98.
This time there was no mistake. His shot making was composed and he looked in control during his 161-ball, 243-minute innings.
In the morning it was more a case of survival, and Tom Latham, sorely out of form, captain Kane Williamson and luckless debutant Neil Broom were undone by high calibre bowling.
You felt for Broom, making his test debut at 33 and after a New Zealand record 136 first-class matches.
His fourth ball, from Rabada, squared him up and wicketkeeper Quinton de Kock took a spectacular catch diving low to his right. It's a tough game at times.
There were soft dismissals either side of lunch before Nicholls and BJ Watling righted the skip with their record 116-run stand for the sixth wicket.
As it happened Nicholls' dismissal, playing over a full ball from J-P Duminy's offspin, started a slump.
Wicketkeeper Watling, who averages 49.5 on this ground, 11 runs more than his overall average, tried to sweep Duminy. The ball bounced off the bottom of his front pad, onto the flap of his back one and up for de Kock without touching the ground. You couldn't pull it off if you tried.
Tim Southee and Jeetan Patel banged on an important 44 in 5.1 overs and the loss of both Stephen Cook and first test centurymaker Dean Elgar to edges caught at second slip certainly put a late spring in New Zealand's step.
Six wickets to the spinners won't have pleased New Zealand. Still, the game is advanced and New Zealand are very much alive. You could say a big day looms - and you'd be bang on.