"I felt sevens wasn't right for me at the time," he explains. "It came down to a gut feeling and purely the desire to wear the All Blacks jersey while being the best 15s player I could be. I had a chance to take this team to another level. It really excited me."
Aaron Cruden started the All Blacks' first Test against Wales in Auckland last June, with Barrett joining the fray at full-back on 43 minutes as the tourists were leading 18-15. New Zealand triumphed 39-21. Barrett was used in a similar manner for the next Test, scoring a try, before finally wearing 10 in the third. He sealed a whitewash with 26 points as Warren Gatland's side were dispatched 46-6.
From there, he cut a swathe through the Rugby Championship and, bar Ireland's famous victory in Chicago, has helped New Zealand through a transition period. In between times, the Hurricanes took a maiden Super Rugby title. Barrett admits Steve Hansen's decision to include him in a revamped leadership group under captain Kieran Read has helped him trust his instincts.
"I guess it was the confidence I got from the chance to drive the team. Steve and Fozzy [Ian Foster] believed in me, which certainly helped. On the field, I just tried not to overthink things. I take a laid-back approach to a lot of things in life and, at the end of the day, rugby's just a game. If you overthink things, you end up doing things without the right reasons in mind.
"The great thing about this team is that we're not conservative. We're encouraged to put ourselves under pressure and deliver plays. It's great."
The All Blacks amassed 80 tries over 14 matches in 2016, suggesting Barrett's management of their attack was pretty effective. But where Owen Farrell and Johnny Sexton - two men sure to be among the British and Irish Lions squad named on Wednesday - are uncompromising generals, confrontation does not come naturally to Barrett.
"That's probably an area where I've got work to do. It's always going to be difficult for me, just because of my personality. I've had to learn how to have those uncomfortable situations that no one really likes to have. But the team vision is always in mind - that's what you're trying to align everyone with."
Punters might point to place-kicking as another weakness in Barrett's game and, undeniably, his percentages are not astronomical. Still, he did not miss a single attempt from the tee in the victories over Ireland and France that ended New Zealand's season. His varied, intelligent kicking from hand was exquisite too, something Barrett knows he will have to lean on when the Lions try to outmuscle their hosts.
"I remember them being over in 2005 and, having experienced northern hemisphere rugby of late, it's going to be huge. We've learned a lot about our game, so perhaps we'll adapt better when they arrive. It's certainly different to Super Rugby and the general way we play down south.
"It's very forward and set piece-orientated. It's often a defensive, tactical game. I wouldn't say it's hugely free-flowing. It's real Test match footy. It's applying pressure. It's hard to explain actually, but it's how you've seen Ireland play in particular.
"For me, It's about getting the balance right. If it's on to kick 10 times out of 10, you keep doing it. You don't stop to think 'we're doing this too much'. You hammer it home. You've got to get the ball into space, and there are many different ways of doing that."
Barrett counts Carter as a mentor who introduced him to the values of yoga and Pilates - "I'm a stiff individual," he concedes. The 25 year-old also calls Carter by acronym 'The G.O.A.T' and can clearly recall the 33-point exhibition in Wellington that sunk the Lions 12 years ago.
"That was freakish. I was in my first year at school and as a young fly-half, I tried to copy everything he did. That was Dezzy at his best."
Is there a stand-out moment?
"Aww...that grubber," Barrett replies, like he is that kid again, excitedly watching Carter's stunning second try for the first time. "How did the ball stay in? What a piece of skill."
According to legend, which Barrett does not deny, his dad Kevin announced his intention to "go breed some All Blacks" following his final game for Taranaki. So far, the dairy farmer has cultivated two. Beauden is excelling and 23 year-old Scott, a mobile, bruising lock with sharp distributing skills, has impressed Hansen in four caps so far. When Beauden's Hurricanes met Scott's Crusaders last season, big brother's conscience was tried.
"It was weird having our skipper Colesy [Dane Coles] digging into him at set piece. While I sort of felt for him, it's a competitive environment."
Jordie, just 20, has joined Beauden at the Hurricanes. He looks like the next All Black cab off the rank. Heftier than his elder sibling, he is turning heads. By the time Beauden was sent off for a second yellow card against the Waratahs on Friday - he is still available to face Sonny Bill Williams' Blues this morning - the pair had scored a try each and generally tortured their Australian opponents.
Fitness-permitting, all three Barretts will face the Lions at least once this summer. But it is Beauden that could be the quiet key to this series.
