The value of the Nonu-Smith partnership is arguably best illustrated by the fact that Sonny Bill Williams hasn't been able to persuade two international coaches to break that combination.
Williams would walk - just about - into any other international side. Coaches would kill for a player of his athleticism and physicality. Yet he's been to two World Cups and confined to a bench role in both.
In 2011, Nonu and Smith were in the fourth year of their partnership. The former was 29, the latter turned 30 during the tournament and if everyone is honest, they thought that would be the crowning moment.
They had formed something special, shown how good they could be, but the odds were stacked against them managing to hold their respective places for much longer.
The midfield is about the most brutal place on the park. The collisions out there are typically between men who are around the 100kg mark. There are bigger athletes on the field for sure, but what marks that area as different is the speed and power of the men.
Nothing happens at walking pace and those who paid attention in physics will no doubt have a memory of equations involving speed, mass and velocity. For those of who didn't pay attention, the point is easy enough to grasp: there's absolute carnage in the midfield and it's a miracle anyone survives for long.
But that's the thing with Nonu and Smith - they kind of are a miracle. Not only have they survived physically, they have reached the 2015 World Cup capable, just about, of playing as well as they did four years ago.
Nonu hasn't changed a bit since 2011. He's the player he's always been - maybe better.
He's guaranteed to hit the ball hard; to spin and bustle and do what he's always done.
There's no indication that he's lost anything. Smith has been a little harder to evaluate.
Some have worried about his influence and whether he's waning but largely that is based on one missed tackle at Twickenham last year.
He was skinned; stood up badly and made to look slow, but it was one incident. Also, not to be forgotten is that a day later he left the tour to attend to a personal issue in New Zealand.
Maybe the peak for these two was 2011 but if they aren't at quite that same level, they are only a fraction off. Williams, who is a better player now than he was four years ago, still can't get the No 12 jersey and the decision to pick Nonu-Smith for this morning's game was never in doubt.
That's what makes their partnership so special - it hasn't been the least bit contentious that they were picked.
"It is not always easy to describe and I am asked about it a lot," says Smith of his partnership with Nonu.
"We always say we started competing for a position and it was really with the encouragement of the All Black coaches to work on the relationship. It probably only started in 2008 when we were selected to start in the midfield and from there we have been fortunate to have had a lot of experiences to learn from.
"Whether you win or lose, or play good games or bad games, the longer you stick together the more you learn about each other and now it is obviously a very healthy relationship. We have played so much footy together and have a good understanding of each other.
"I know what help he needs things on and how he is feeling in a game and he does the same with me so it is obviously a great asset to play alongside someone who knows you so well."
This morning was their 60th test together. It could have been their last, but no one is thinking like that. And the reason no one is thinking like that is because they have retained their confidence in a partnership whose value should never be taken for granted.
