They look at his feet and are aware that he can step and swerve and that in confined spaces, he can dance free. But his lack of size makes many think he's not actually all that fast on the open toad as it were.
He is and he showed that in Sydney when he was able to get in support of Ioane after Barrett had stripped Michael Hooper to create a turnover attack down the left wing.
McKenzie can therefore not only bamboozle defenders, he can get on the outside of them as well and he'd be about one of the quickest outside backs there has been in recent years.
Ioane is quicker. He has genuine pace and is the fastest in the squad and one of the faster All Blacks of the professional era.
He's shown this year just how quick he is. The first example came playing for the Blues against the British & Irish Lions when he put daylight on the defence when he had a half chance.
He did it again in the test when he latched on to a loose ball and then cruised past Elliot Daly without the need to even fend. And then there was the way he stood up Israel Folau in Sydney. That was special.
Few, maybe no other, wing in world rugby would have been able to do that. Ioane, from a standing start, was able to get outside Folau and score in the corner.
The youngster reckoned it was only because the Wallaby fullback was impeded by a divot in the ground but his kindness in saying that felt like it was driven by a desire to protect the reputation of a special player.
Ioane is super quick and that's largely why he's in the team. His pace creates options and that's why the All Blacks were looking to run from everywhere in Sydney.
They know that if they can use McKenzie and Ioane deep inside their own territory, they will pull a defence to breaking point. Smith and Barrett can then be used bringing the attack back the other way and it's all too much for the opposition to shut down.
That's why the Wallabies were torn to shreds in Sydney. They were simply unable to cope with the pace of the attacks and this sort of rugby is no doubt going to be developed by the All Blacks throughout this year and with a view to perfecting it at the next World Cup.