Aaron Smith has been, arguably, the world's best No 9 this year, but he's played a huge amount of rugby. The aerobic demands of the position are exacting and this deep into the season it would be prudent in the next few weeks to inject Kerr-Barlow into games earlier.
For Whitelock and Toomaga-Allen, tomorrow will give a taste: something for them to savour over the summer. They are both longer-term projects - men who will be asked to refine and hone their work over the next year so they can become squad regulars.
The hardest to place is Halai - who despite the fact he'll be wearing No 11 tomorrow, will be on the right wing. The blockages ahead of him are severe: Cory Jane was probably the world's best wing last year; Ben Smith has taken this mantle this year.
So what chance of Halai ousting either of those two? What chance of Halai even becoming a squad regular next year? It's an almost crazy thought that he could become a regular starter - given that this time last year he was the major surprise to have made the Blues squad.
But at 1.95m and 110kg, Halai is a totally different player to Smith and Jane. He has raw power they don't. He has the ability to run over the top of people which they don't and he's also got the most room for growth.
"He's grown his game a heck of a lot," says head coach Steve Hansen.
"He's improved immensely aerially. He's a shy guy and he's played shy probably in the past. He's managing now to play the way he would like to and the way we would like him to. He's confident on the park and at displaying the skills he's got."