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Part of Barrett's contract with New Zealand Rugby (NZR) allows him to play a sabbatical overseas, and the two-time World Rugby Player of the Year has joined Suntory for the 2021 Top League season, which begins next week.
Despite taking a year out from Super Rugby and the spotlight of playing at home, the 29-year-old is eager to impress All Blacks boss Ian Foster and claim the No 10 jersey, having featured heavily at fullback (No 15) in recent years.
"I have got a little bit of work to do in terms of slotting back into that role (first five-eighth)," Barrett told reporters.
"I think one would expect me to play a little more at number 10 and that is certainly something I am aspiring to do back in New Zealand for the All Blacks."
Barrett is one of a number of high-profile foreign players who have joined Japanese clubs this season, including compatriots Kieran Read, Ben Smith and TJ Perenara.
Barrett could have chosen to play a season in France where, as a non-exempt foreign-based player, he would have ruled himself out for contention for the All Blacks. But he chose Japan in large part because that would allow him to better prepare for the 2023 Rugby World Cup.
"It isn’t Japan versus France at all. It was about 2023," Barrett said.
"I am really happy about the decision that I made."
Top League, which was completely scrapped last year because of the coronavirus pandemic, is due to begin next weekend and Barrett said all the players were prepared to be flexible should the virus disrupt the league schedule.
Since arriving in Japan late last year, Barrett has also been working on his Japanese and was asked to say a few words on Wednesday.
He mustered a few phrases, much to the pleasure of the Japanese media.
"Gosh, I have been put on the spot," he said. "I promise you I am better (at Japanese) than what I am presenting right now."