New Zealand have only qualified for the World Cup finals once before, in 1982, but are suddenly on the verge of making a second appearance.
They drew 0-0 away to Bahrain in Manama last month, leaving everything to play for in Saturday's return leg at Wellington's Westpac stadium.
The expectation in rugby-mad New Zealand is rising by the day and even Nelsen and Herbert admitted they were struggling to contain their excitement.
"There is nothing bigger," Nelsen told reporters in Wellington.
"It's bigger than the Olympics 100 metres final...I've just put a bit more pressure on us haven't I?"
Herbert, a mainstay in the centre of defence in the All Whites side that qualified for the 1982 finals, said he was also caught up in the excitment.
"It's the biggest sporting event in the world and to be able to be part of that is something that is very exciting," he said.
"We want to deliver another World Cup opportunity for the country. We have got a great balanced side. There is a lot of experience and there is a lot of feeling around that."
The game has sold out with capacity increased by 1,000 temporary seats to 35,500 to make it the largest crowd to watch a football match in New Zealand.
More than 17,000 tickets were sold in less than five days following last month's scoreless draw and Herbert said he was overawed by the public response.
"I think as it has got closer, and with the way we have brought the tie home there is added pressure, but why wouldn't there be? This is the industry we're in and that's the level of competition we're aiming to be part of.
"The stadium is full, so it has captured a lot of people's imagination and I would guess that a lot of people will be non-football people."
New Zealand earned their spot in the playoffs after winning the Oceania qualifying division, a task made somewhat easier after Australia defected to the Asian Football Confederation.
Bahrain, who have never qualified for the World Cup finals but made the playoffs four years ago, finished fifth in the Asian qualifiers.
"It has been a while since we had an audience like this, but great. I think that's the sign of the times for the team. And quite rightly they deserve it," Herbert said.
"The nation is right behind the team and people sense a fantastic chance for a team to be back on the world stage.
"To go to the World Cup would be an incredible feat."
