He's not a maverick as such. He doesn't play outside team protocol or suit himself how he attacks and defends. That's not it. That's not him. He works within the patterns yet manages a way to execute the unthinkable without it seeming to have been an enormous risk.
That's what throws defences - they think they can see what is coming and only realise too late that it wasn't quite what they expected.
Never was there a better example of his insane unpredictability combining with his natural gifts than the try he scored against Ireland in Dublin last year. It was direct from first phase ball - Aaron Smith fired the pass from a scrum and Barrett found a way to get on the outside of Conor Murray and score from 45 metres without an Irish hand being laid on him.
How does that happen in modern rugby - a try like that from first phase? It happened because Barrett has the big five of pace, agility, vision, phenomenal skill and confidence.
There's more to him than that, though. He is greater than the sum of his collective parts. He will try what no one else will and nine times out of 10, he pulls it off.
Barrett has a gift to make things happen and break even the tightest defences. Hurricanes coach Chris Boyd said earlier this year after Barrett had been magnificent against the Blues that the first-five is going to bring seven to 14 points to every game he plays simply by being himself.
It seemed like a fair value estimate of Barrett who even at test level seems to either create or score at least one try per game purely on the back of his outrageous ability.
This is the bit the Lions have to reconcile. They have built a stunningly effective defensive system on this tour. They have generated incredible linespeed and been quite masterful - the test team at least - at shutting down opponents and squeezing the life out of them.
They are planning to do the same to the All Blacks at Eden Park and yet it feels like they are only kidding themselves a little bit if they think they can contain Barrett for 80 minutes.
He will find a way through their defence, be it from first receiver or from the back field.
Barrett will manufacture some kind of unexpected business that the Lions can't shut down or if they do, not before it has created another hole somewhere else.
Big games tend to always have defining plays and defining players. The Lions would love for it to Murray or Owen Farrell, but as good as they are, they are bringing the conventional to this series.
They are phenomenally good conventional skills but conventional nonetheless. Barrett on the other hand is bringing something entirely different - a skill set that has a conventional theme but utterly unconventional application.
He mentioned on Thursday that he has distinct memories of the last Lions tour to New Zealand. What he remembered from 2005 was the performance of Carter and maybe there was just a flicker of something behind his eyes as he said it.
Maybe there was a realisation within himself that New Zealand's next once-in-a-generation first-five could be inspired by him and the role he plays in this Lions series.
