Barrett said he felt a shift in attitude among the Blues when returning from Japan last year and training with the side for a few weeks.
"Vern's [Cotter] edge, his difference, his style of the way that you saw the Blues played last year, is different to what New Zealand's experienced in recent times.
"The boys have enjoyed that."
The concentration now is on the first pre-season game this week against the Crusaders at Kirwee, but they were also aware that they'll be lining out against the Chiefs at Eden Park in two weeks.
"We're going to have to be ready for that and we're working hard and building up for that huge occasion."
Barrett said the most significant growth he has noticed in the team is in the leadership of experienced players like Patrick Tuipulotu, Dalton Papali'i, Rieko Ioane, and others. That was the sort of thing that would prevent any complacency developing among the defending champions.
Another development he saw was the tough edge the forwards presented and the way everyone in the side was prepared to roll up their sleeves and contribute to the hard work required.
"It's been a fairly blunt strategy that's worked, and we'll look to adapt a little bit. We can't just assume that that's going to work again this year.
"We'll have to improvise and not be complacent."
He was introduced to the Cotter method in December when an intended 10-minute meeting turned into a 90-minute meeting.
"It's obvious what Vern's approach is and he is keen to grow the game. That's something I'm keen to collaborate with. We've got to be a little bit better too."
Barrett was also aware of Harry Plummer's progress in leading the side from first five-eighths, and there was competition for the position and all positions throughout the side.
"We know that depth is going to be critical. It's healthy competition that makes us better. But it's a long season, there are going to be injuries, so everyone needs to stand up when we get our opportunity."
Having the Chiefs first up and the possibility of a meeting with All Blacks contender Damian McKenzie is an early challenge should he get the start.
"I enjoy going head to head with my mate and more importantly it is a rematch from last year's final. They probably want a little bit of revenge. If I'm part of the team I'm excited to get back into it."
Barrett also expects greater strength from Australian sides this year.
"The likes of the Waratahs, or all the Australian teams have benefited from Rebels players going to other teams. Naturally, you'll see those teams get stronger."
Starting the season at 33, Barrett said time has given him a more holistic approach to life, perspective with his family, and where he expends his energy.
"Things like recovery are so important, nutrition, all of that. When I come to training, I still want to feel like the 23-year-old I once was and to give as much as I can to this team."