Barrett is the beating heart of the All Blacks' attack. He is the most devastating attacking force in world rugby but he needs to be working his magic at first receiver and behind a pack that at least has physical parity.
Lions coach Warren Gatland has said a few times that he doesn't feel the All Blacks have stressed his side's defence in the series so far. It's an exaggeration, but there is foundation to his point.
The All Blacks haven't attacked with the cohesion and creativity that they expect. It's not that they haven't stressed the Lions defence, they just haven't done it enough.
Last year the All Blacks were averaging more than five tries per game and blowing teams away with the speed and width of their attack. It was rugby's version of Blitzkrieg - the All Blacks using so much heavy artillery that defensively teams couldn't cope.
In the middle of it all was Barrett. He himself was usually the most potent threat - so quick, so alive to opportunity and so intuitive when to take it. If he didn't just take the hole himself he got far enough into it to play a teammate the rest of the way through it.
The All Blacks flowed and no one could stop them. They were pass and catch masters - their continuity a thing of astounding beauty at times.
But two tests into this series and they haven't been the same force. Gatland is right in his premise that the All Blacks haven't achieved what they wanted.
But he's possibly wrong to imply, which his statement does, that the All Blacks are in some way not the same team they were last year or that if they are, they can't find a way to be so against his Lions.
He's inviting a response he may not like from the All Blacks, because it would be reasonable to assume all they need to ignite is to keep 15 men on the field and Barrett at No 10 for 80 minutes.
The focus for the All Blacks this week has been getting back to doing what they do best. And that's knocking teams off their feet with lightning attacks that are built on speed of movement, quality of execution and breadth of vision.
Barrett hasn't forgotten how to orchestrate all that - he just hasn't had the chance to do it. He was in dangerously good form before the series and it would be a surprise if he doesn't provide a timely reminder of that some time before the Lions leave New Zealand.