So, when Munro was elevated to open in Nicholls' absence, and the pair strolled out onto a wicket still green and dangerous after Sri Lanka had been rolled for 136, skepticism about how the pair would fare would have been understandable.
Instead, the duo added more runs than they had in their last nine partnerships combined, overcoming some early jitters to crush the unthreatening Sri Lankan attack around the Sophia Gardens ground.
They did have the benefit of having won the toss – neither opener seemed particularly keen on the prospect of batting first on the green deck – but Guptill says it wouldn't have changed their attacking nature.
"I think it worked in our favour a wee bit. But even if we had been put [into bat] this morning, I think we still would've played with the positive intent that we this afternoon. It may not have come off, but we still would've gone out there and tried to play as positively as possible."
That positive approach is something that the Black Caps will need to maximise if they're to match some of the powerful batting lineups possessed by other Cup contenders, and Munro was delighted to have finally hit a one-day milestone with his good friend.
"A perfect start – Guppy and I had done it for Auckland for so long, and in Twenty20 cricket for New Zealand we've got 100-run partnerships and had things go our way. But to do it in a World Cup, and our first 100-run partnership in this format of the game – it's awesome.
"We feed off each other really well and we've got a good relationship on and off the field. People always ask 'is it me vs Guppy up the top?' and no – it's a partnership, and to be no wickets down at the end there is very pleasing from a team perspective but also personally as well."
Whether the pair can be a sustainable partnership for the entire Cup is still a pertinent question, with better bowling attacks sure to test their resolve. Nicholls, too, will want to have a say upon his return.
But now – at long last – the Black Caps have a platform to build from at the top of the order.