Indeed, the significance of today's match goes deeper than just the link back to that semifinal.
Du Plessis pondered the question a moment before admitting this may be the most important ODI for South Africa since that clash two years ago.
Their eyes have been on the Champions Trophy in England in June since they arrived here. But their No1 ODI standing is also on the line.
The calculations are perplexing but in seems a 3-2 win in this series will elevate them back above Australia.
New Zealand will stay third, win or lose today.
"Definitely from a pressure point of view this is the one that has the most value to it," du Plessis said of their recent series. "[The last two] series have gone 5-0, 5-0 [home to Australia and Sri Lanka] so for the relevance of getting into the big moment, this is big."
Certain assumptions can be made.
AB de Villiers shapes as the biggest threat to New Zealand with the bat. Consider the skipper averages 203 against New Zealand in ODIs in this country, just once in 11 innings falling below 30. Yet not one South African has scored a century in the four games so far. New Zealand have mustered two.
Martin Guptill, on the back of his stunning 180 not out in Hamilton, appeals as potentially New Zealand's most influential batsman, the presence of captain Kane Williamson and senior man Ross Taylor notwithstanding. His ability to get the board turning early is crucial.
Du Plessis paid due tribute to Guptill's innings yesterday and was confident New Zealand would have been seriously challenged to chase down the target of 280 without that thunderous contribution, a view no one would argue with.
"New Zealand are a team who play the big moments really well," du Plessis said, adding that in his estimation South Africa have been firing at about 65 per cent during the series.
Senior seamer Tim Southee believes his team have more to offer than they've shown so far, too. There have been misfires for both teams but Southee suspects home advantage might count for a bit more at Eden Park, with its peculiar dimensions, than it does at most other grounds.
How New Zealand, and particularly Southee and Trent Boult, cope in the death bowling phase shapes as a key element today.
The pair, News Zealand's best new ball operators, went for a combined 140 runs from their 20 overs in Hamilton, as de Villiers took charge.
Southee admitted it had been a "mixed bag" for New Zealand in the series. As he put it cryptically: when you have a batsman "who can hit you 360 degrees at will at the end, it is difficult".
South Africa seem unlikely to vary their XI greatly although they might try to find a place for the talented bowling allrounder Andile Phehlukwayo.
It will be interesting to see how New Zealand shuffle their cards. They could be inclined to stick with their XI from Hamilton, but Lockie Ferguson's extra pace on a bouncy pitch may give pause for thought.
A crowd of 22,000-25,000 is expected.
Just another ODI game? Think again.
NZ v South Africa
Fifth ODI, Eden Park, 2pm today
New Zealand
(from) Kane Williamson (c), Martin Guptill, Dean Brownlie, Tom Latham, Ross Taylor, Luke Ronchi, Jimmy Neesham, Mitchell Santner, Colin de Grandhomme, Jeetan Patel, Tim Southee, Ish Sodhi, Lockie Ferguson, Trent Boult, Matt Henry.
South Africa
(from) AB de Villiers (c), Hashim Amla, Quinton de Kock, Faf du Plessis, J-P Duminy, David Miller, Farhaan Behardien, Dwaine Pretorius, Chris Morris, Wayne Parnell, Andile Phehlukwayo, Imran Tahir, Tabraiz Shamsi, Dane Paterson, Kagiso Rabada.
