Not least in 2011 when the All Blacks were down to their fourth-choice fly-half in Stephen Donald but still held on to win a tense final against France in Auckland.
And while New Zealand are the dominant force in world rugby, with only three defeats since that night in Auckland four years ago, Nonu is taking nothing for granted.
"We saw in the last World Cup with our injuries at No.10 ... [before] our last pool game. I think for this World Cup, our side we just look at it day by day, really," said the centre.
"It's the same in terms of being a test match, but Rugby World Cup is totally a different level. It's the pinnacle of your rugby career, making it to a World Cup.
"Every game is special in terms of making it towards the end. Your prep has to be right and you have to play the best you can every match."
The All Blacks open up their campaign up against Argentina at Wembley on Sunday, a side they beat in Christchurch two months ago in the Rugby Championship.
But Nonu admits that victory will count for little when battle begins on Sunday.
"They put up a fight in Christchurch, they were really physical and put up a good defensive line in terms of when we played them. They can roll anyone, especially at World Cups," he added.
"When you play different sides, you don't know what you are going to come up against. You can study clips of what previous games you've seen your opposition play, but they may put out something else."
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