Wallabies captain Michael Hooper would love to see Japan play more international Tests, but says rugby's various governing bodies need to be careful not to burn out players in the process.
Japan hasn't played an international since the 2019 World Cup, when they made it to the quarter-finals before being knocked out by South Africa.
Hooper is currently in Japan on a rugby sabbatical playing for Top League side Toyota Verblitz.
The 29-year-old has been impressed by the hunger displayed by Japanese players in their bid to learn and improve.
The Wallabies regularly play southern hemisphere rivals New Zealand, South Africa, and Argentina, while the Six Nations features the best countries in Europe.
But Japan have struggled to get consistent fixtures against rugby heavyweights.
Hooper feels ideas need to be explored to address that, but he says governing bodies need to be careful not to over burden players from other nations with too many extra Tests.
"There's concern if you up the amount of Test matches," Hooper said.
"You won't see players go super deep into their careers. It does take a toll on your body physically and mentally. Mentally due to the travel, picking yourself up physically, battling through time away from home.
"It (the burden on a player) is multi layered - not just how many minutes you play on the weekend. Getting it right is so key."
Hooper's advice comes as the All Blacks prepare to play 15 Tests in 2021, COVID-19 pending.
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"The plan at the moment is 15 test matches and I'm not sure if the All Blacks have ever played 15 Test matches [in a year], so it's pretty big," All Blacks coach Ian Foster told Sky Sport's The Breakdown. "So we're in the process of working our way through that and clearly there'll be checkpoints as we go along, based on borders because obviously the border opening are going to be key for us later in the year.
"So we'll be keeping an eye on that, keeping an eye on plans, and ultimately there will be some other plans that if borders get shut down, but there is a desire to play a lot of rugby. And who knows, we might even end up with a whole lot of countries in one country playing a mini-World Cup...but who knows what's going to happen. But I do know we've got a big year planned."
Former All Blacks star Kieran Read, who is Hooper's teammate at Toyota, would like to see Japan placed in an international competition so they get regular games.
"They're arguably one of the top eight sides in the world now after the World Cup. The fact they haven't been able to play any footy since then is a shame," Read said.
"Hopefully we can give them a chance to play some international footy. The only way you can get better is to play those top sides more regularly."
Hooper feels an IPL-style tournament in Japan could be a way to grow the game.
"You can get more guys from Europe coming down, and players coming up from the Southern Hemisphere," Hooper said.
"There's plenty of ideas out there, it's whether we can execute them and whether they're reasonable within the already busy schedule."
Hooper is being coached at Toyota by former Waratahs assistant Simon Cron.
Both he and Read have been impressed by Cron's work there.
"I've seen a growth in him since I was last coached by him, which was midway through 2019," Hooper said.
"His knowledge of the game is so great."