Nelsen, lounging back in his chair, and Herbert, leaning eagerly forward, both said nervousness was not a factor in the lead up to the game tomorrow morning (NZT).
In fact, they felt more pressure to perform before the World Cup qualifier against Bahrain in Wellington last November, which they won 1-0 to advance to the sport's global showpiece for the first time since 1982.
"I think it showed against Slovakia," Nelsen said.
"None of (the All Whites) were worried or showed any signs of nerves, held it together well, and got a result (1-1 draw).
"It could be Italy, it could be Brazil, it could be the greatest team in the history of sport. I don't think nerves will be a major factor to tell you the truth."
New Zealand's underdogs status -- as the team considered by the bookies to be the least likely to win the World Cup next to North Korea -- is a strength rather than a weakness, Nelsen said.
"That's one thing you don't normally have to do, is motivate an underdog,.
"We are playing against the world champs in a World Cup, a chance to essentially go through to the next round."
Nelsen said his team put themselves in a very good position after drawing with Slovakia and it was "up to the soccer God" to decide the result tomorrow.
"We are fairly well prepared and well organised and no matter what happens in the game the boys will be giving everything."
New Zealand proved they were worthy of playing on the same field as Italy when they lost 3-4 to them in a friendly ahead of the Confederations Cup in South Africa last year.
"Whatever the outcome, there is still a chance going into round three," Herbert said, eyeing their final group F match against Paraguay at Polokwane on Friday (NZT) as an opportunity to earn more points.
Herbert will field the same starting 11 tomorrow who drew with Slovakia in Rustenburg, with vice-captain and midfielder Tim Brown missing out again as he recovers from a fractured shoulder.
"I don't think we would have any hesitation if we needed to use him now," Herbert said.
"Paraguay is probably a better target from him. He has made some great strides."
Herbert admits his team will be under added pressure with New Zealand Prime Minister John Key watching their game at Nelspruit's Mbombela Stadium, but at the same time that kind of support was what had kept his players motivated.
"Four or five years of building a football team that's shaken the nation is fantastic. And the players are getting accolades that they certainly deserve."
