'My No. 1 knock' - Guptill on his 180 not out
It was a performance he rated as probably his best ODI innings, which would put it ahead of his 237 in the World Cup quarter-final against West Indies, because it came off the back of a month on the sidelines with a hamstring injury. That was a sentiment supported by his captain Kane Williamson who termed it a "world-class" innings.
Guptill had only begun netting a week ago, and the session the day before the fourth ODI was the highest intensity he had trained at since injuring his hamstring before the one-off T20I against South Africa, which followed a previous hamstring strain during the home Chappell-Hadlee series. In all, Guptill has only batted three times in 2017, twice for New Zealand and once for Auckland: his scores 112, 61 and 180 not out.
He had spoken before this match of hoping that he could regain the rhythm he had earlier in the season. The outcome was a magnificent display of clean hitting which included 11 sixes and left him with New Zealand's three highest scores in 50-over cricket.
"It's pretty up there, possibly No.1. I'm reasonably happy with how today went without a lot of preparation," he said. "It was difficult to bat all round, two-paced, turning, slower balls gripping, it wasn't easy, and I wanted to create a good partnership. I did that reasonably well and fortunately I was able to get a few out of the middle."
He had immediately jumped in an ice bath after the match and said his hamstrings were "a bit tight" but nothing that wasn't to be expected.
The two camps differed somewhat on how the conditions panned out with AB de Villiers believing the surface eased, starting at the back end of South Africa's innings when they scored 100 off the last eight overs, but Williamson supported Guptill's view that it remained a tricky pitch throughout.
"I said to Martin when he came off, that's probably his best, and he's done it a few times to be fair so there are a few tight comparisons," Williamson said. "In a chasing effort on what wasn't an easy surface and to hit the ball the way he did and play with the freedom we know he can and do something special against the best team in the world was a special, world-class effort."
In a chase of 280, Guptill inside-edged his first ball from Kagiso Rabada past the stumps, played out a maiden from Wayne Parnell in the second over and was 2 off 10 balls when he connected with a stinging pull shot off the left-arm quick for the first of his sixes. The splits for his fifties were 38 balls, 44 and 41 with his last 30 runs taking 15 deliveries.
"I wanted to give myself a chance really, have a look at what it was doing," he said. "I got a few away and developed a strike rate early at the top and carried it through."
Guptill's innings continued an upturn in his fortunes against South Africa. In the previous one-day series between the teams, Guptill scored his first hundred against them in the second match in Potchefstroom having had a previous best of 58 from 12 innings at an average of 14.50. In the space of three innings, the average against South Africa has lifted to 35.92.
"I've always rated him as a player, he's had to work through a few things," de Villiers said. "I was always hoping this day would never come, where he's figured out his game, playing it nice and late and he's moving well. I could sit here for quite some time and talk about that knock. It was a very special innings."
Andrew McGlashan is a deputy editor at ESPNcricinfo