Dan Carter believes the biggest tests are still to come for the All Blacks with less than a year until their World Cup defence.
The All Blacks legend moved to Kobelco Steelers at the end of last season and was speaking ahead of New Zealand's Bledisloe Cup match against Australia in Yokohama on Saturday, live on Sky Sports Action at 7am.
New Zealand recently stumbled after their shock home defeat to South Africa in the Rugby Championship, and the 36-year-old thinks this is a sign of the increased level of competition heading into next year's World Cup in Japan.
Carter, who was instrumental in the All Blacks' World Cup triumph three years ago, said: "They're a fantastic team and I think they've grown from 2015 and I think the World Cup is going to be their big test. Historically post-World Cup, a lot of teams struggle through a bit of a rebuilding phase and the All Blacks didn't do that.
"That's why they were so dominant in the first couple of years. Now teams are starting to find form and consistency and the competition for the All Blacks is so much stronger than it was a year or two ago.
"I've been hugely impressed with the current All Blacks side and what they've been able to achieve.
"They've done extremely well over the last couple of years, but as the competition gets better and we move closer to the World Cup I think that will be the real test to see exactly where this team is at. I'm confident they'll be even stronger in 12 months than they are now."
Carter believes staging Saturday's clash between Australia and New Zealand in Japan is a boost for the country in the build-up to next year's World Cup and is expecting a full-blooded encounter between the teams.
"They've got some quality rugby here in the top league but what they're missing is that really high level international game on a regular basis," the former Racing 92 fly-half said. "To have a couple of Test matches like the Bledisloe Cup game and the All Blacks playing Japan; there's some real high-quality rugby.
"Speaking as an ex-All Black, there's no dead-rubber match against Australia and after losing to them in the third Test match last year when we had wrapped up the Bledisloe Cup there will be a little bit of an edge to this game to make sure we don't repeat last year's performance.
"I'm expecting some really exciting, high level international rugby so it's exciting for the Japanese fans."
Since Carter ended his international career, Beauden Barrett has established himself as a world class fly-half for the All Blacks. Carter was never in any doubt about his ability and insists it was only a case of waiting for a chance to flourish on a regular basis for the world champions.
"He was always a world class rugby player even when I was playing alongside him and you knew just what a talent he was.
"Finally he's got his opportunity in the last couple of years and he's just taken it and taken his game to a new level. He's now directing and leading the backline and being one of the key figures of that team.
"He's really impressed me just with his leadership and obviously we all know how fast he is and with his skills he can just turn a game just like that. You can never relax because magical play from him just totally changes the game."
It is less than 12 months until the start of the World Cup in Japan and Carter, having settled into his new rugby home, has noticed an increased sense of anticipation ahead of the tournament.
He said: "I've been here five or six times now and every time I've been to Japan there's been a little bit more interest in rugby and this time you can definitely sense it's only 12 months away.
"A couple of games I've been involved in there has been a sell-out crowd and just as much media afterwards as a Test match, so because of that I think rugby is really growing and heading in the right direction. It's very exciting and it's an amazing opportunity for Japan to showcase their beautiful country."
England face New Zealand for the first time in four years next month, live on Sky Sports, with Carter impressed by the spine of Eddie Jones' squad - particularly their backline.
"There's so many world class players and what's impressed me about England's team is they've got competition and depth they potentially didn't have a few years ago or even before the World Cup.
"You've got Elliot Daly, Anthony Watson and the absolute game breakers. I was really impressed with them during the Lions series and Owen Farrell is world class. He's a key member of that side for leadership and his competitiveness.
"They are real key members of the England side although obviously you can't do it without the forward pack."