1) McKenzie has a little way to go in his defensive game. A lot has been made of his try-saving tackle on cathedral-sized Crusaders wing Nemani Nadolo but he has fallen off other tackles.
2) Opponents are starting to work him out. They have toned down the kicking game to the Chiefs' back three and muscle up on him quickly when he has the ball. At top level, at fullback, his size means he has to go trampoline-high to get the ball if he is being targeted, as the Australians and South Africans, for example, are sure to do.
Neither reason is enough to keep him out of the All Blacks long-term. Another small man, Aaron Cruden, had similar deficiencies in his defensive game and he tidied them up well.
Most McKenzie fans see him as a natural replacement for World Cup will-o-the-wisp Nehe Milner-Skudder. They are similar players with McKenzie perhaps having the edge in sheer pace. He can also play first five-eighths, wing or fullback and has been the best goalkicker on show in the New Zealand franchises.
There is also the issue of squeezing in the All Blacks door ahead of players in whom the coaches have confidence. It's dollars to doughnuts Cruden will be the All Black No 10. There is an opening on the wing with injuries to Milner-Skudder and Waisake Naholo (although the latter is now back on the field). Many think the best selection is moving Ben Smith there and McKenzie into fullback.
However, there's this world-class fullback called Israel Dagg who has been exhibiting signs of returning to his best. Still only 27, Dagg's return to the international field may be of more benefit to the All Blacks selectors than injecting McKenzie at this point.
Many also think McKenzie might be best off the bench. But where does that leave Beauden Barrett? He's also had a fine season and has proven credentials in - oh, I don't know ... the World Cup final - covering 10 and 15. So no room for McKenzie right now.
The other interesting selections are at loose forward and midfield. It now seems more likely the selectors may feel it's time for someone other than Jerome Kaino to have consistent time in the No 6 jersey. There are plenty of claims for the Highlanders' Elliot Dixon or the Hurricanes' Brad Shields but my money's on Steven Luatua. He can play 6, 8 or lock, is a proven lineout option (as Richie McCaw was) and is looking much more the player he was when he got into the All Blacks the first time.
Sam Cane will be openside flanker but who will be his back-up? Matt Todd has benefitted from the Crusaders' good Super Rugby campaign but this could be the time, given he has surrendered his Olympic sevens hopes, for Ardie Savea. He's got more to learn than Todd has about ball-pilfering but Wales seem a good opportunity to try him at the next level.
In the midfield, it seems certain the selectors will go for Ryan Crotty at second-five. Replacing Conrad Smith's unparalleled distribution and ability to read a game and centre's defensive complexities is one of their biggest headaches. While Crotty is usually a 12 rather than a 13, Malaki Fekitoa's positioning at 12 against the Chiefs may be a possibility for the national team if they are seeking to replicate the pairing of the free-running Ma'a Nonu and the strategic Smith.
Either way, the Chiefs' Charlie Ngatai may not make the starting selection, although I'd expect him to be in the 23. He is too good an attacker and distributor and has a fine kicking game.
So the first All Black team for the series against Wales could be: Owen Franks, Dane Coles, Joe Moody, Brodie Retallick, Sam Whitelock, Steven Luatua, Sam Cane, Kieran Read (c), Aaron Smith, Aaron Cruden, Julian Savea, Ryan Crotty, Malaki Fekitoa, Ben Smith, Israel Dagg. Bench: Codie Taylor, Charlie Faumuina, Wyatt Crockett, Patrick Tuipulotu, Ardie Savea, Brad Weber, Beauden Barrett, Charlie Ngatai.