Coach Clayton McMillan said McKenzie hadn't missed a trick as the Chiefs got a 27-10 lead at halftime. But the Crusaders got a good hit on him, and he was hurting.
"It was sore at halftime, but he felt confident and wanted to go out there, but he shied away from a little bit of contact which indicated he wasn't 100 percent."
McMillan said the forwards' effort in being direct allowed first five-eighths Damian McKenzie to help the backline show its potential.
"He [McKenzie] didn't miss a trick tonight, but they got a good one on him so he's hurting, but he'll bounce back."
Captain Luke Jacobson said having to withstand the Crusaders' second-half comeback was unsurprising.
"We talked all week that it was going to take 81 minutes. We probably had things our way in the first half, and at the start of the second half, we did not have the intent we would have liked.
"We found ourselves under the goalposts a couple of times but fought back well to gain a little momentum and then just ground it out."
McMillan said the issue with the new mouthguards was complex when centre Anton Lienert-Brown was forced from the field for an HIA because it affected them when the game was in the balance.
"You're making decisions around, do you exhaust your bench, could it go to extra time, do we need to save somebody? And those decisions got taken away from us because of the injuries to [second five-eighths] Quinn Tupaea."
But he said the mouthguards were intended as another mechanism to protect players.
He was happy to secure the win, especially with the first half, where the set-piece was accurate and the side enjoyed a lot of possession and momentum. They had lost that in the second half, but the lesson from that was the importance of getting some back-to-back moments to regain momentum.
The Crusaders won some scrums and applied pressure through contestable kicks. They could keep the game alive, and when players like captain Scott Barrett went to another gear, the others followed.
"We need to figure out, or understand, that when we lose momentum, there are things we can do to get it back.
"We never really got that going until the last five or 10 minutes. We tried to force play."
But the recovery was an example that the group was maturing and could fight through tough exchanges. And that was the most pleasing aspect of the win.