When the time comes to make the choice, it won't be easy for the selectors or the players. Take the case of Messam; he hasn't done much wrong and yet who doesn't have a sense ahead of this match that he may be about to rescind his No6 jersey to Kaino?
Messam was the players' choice as their man of the Rugby Championship last year. His work rate, his tackling, his physicality - they were at a level that many previously thought he'd never reach. He played exactly as an All Blacks blindside should.
Even last week, while he was quiet, he got stuck in and other than that scrum faux pas where he was caught napping by England No 8 Ben Morgan, it was hard to be overly critical of his performance.
But next to him in the boot of the scrum, there was this "caged beast". Messam himself acknowledged that Kaino made a sensational return to test rugby. What impresses so much is his ability to stay on his feet when he carries the ball into contact and without fail snatches extra metres.
If Kaino plays as well again in Dunedin he'll have to be rewarded with a No 6 shirt in Hamilton.
It's the same for the back three and Ben Smith in particular. What if he rampages all over Forsyth Barr Stadium - as he has most weeks for the past two years - in his preferred fullback role?
There is a strong case to be made that he should stay there in Hamilton. Smith has been one of the most consistent All Blacks performers of the past 18 months and using him at fullback provides more opportunity for him to get his hands on the ball. Keeping Smith at fullback could also provide Dagg with a sharp incentive to rediscover his true self.
Dagg hasn't fired yet at any point this year. He's not so far away from solid form but he is that little bit off - maybe because of the niggle he has been carrying or maybe not.
The problem for him is that his trump card - his booming kicking game - has been compromised by his thigh injury. Give him another week off and let him bristle at seeing someone else in the jersey he covets.
