New Zealand captain Ryan Nelsen believes the Wellington Phoenix hold the key to the national team's World Cup qualifying chances.

The All Whites face Bahrain in Wellington this Saturday in the do-or-die qualifier and Nelsen, the Blackburn Rovers defender, is confident having almost half the Phoenix line-up playing in front of home fans will be a major plus.

"Obviously the 35,000 Kiwi fans are hopefully going to be screaming and chanting and going crazy come Saturday and I think that's going to be a huge advantage for us," Nelsen said.

"I think also for the Wellington boys it's their home field and they have got a formidable record there at home. They know every blade of that grass and those boys are going to be key for us. There are some great advantages for us.

"Obviously the cold hard facts are that Bahrain have played 20-odd games and are extremely well funded. That's life but we're extremely positive heading into this game."

Nelsen said it would be enormous if the Kiwis were able to qualify for the world's biggest sporting tournament for just the second time in history.

"There are more people watching that than the Olympics. There are more people watching that than anything on the sporting planet," added Nelsen.

"To get to a sporting event like this, in general I think most people understand that it's fairly big. In terms of playing in it and for coaches and management team it's the absolute pinnacle in all sport. There is nothing bigger.

"This is bigger than the Olympics 100m final if you get to it and potentially go on. If you win the World Cup in football there is absolutely nothing on this earth bigger than that."