Former Japan captain Takuro Miuchi and ex-France flyhalf Frederic Michalak welcomed World Rugby's proposed "League of Nations" but cautioned Thursday issues such as player burnout and the timing of the domestic Top League needed to be addressed.

"You have to look at the number of games players are expected to play in a season," Miuchi said at the Foreign Correspondents' Club of Japan, in Tokyo.

"And there could be some problems trying to adjust the Japanese domestic league around the event. But the experience of competing against other countries will be invaluable for Japanese players."

The proposed tournament, discussed by rugby leaders this week in Los Angeles, would see Fiji and Japan joining sides from the Six Nations and Rugby Championship in a 12-team league.

Teams would play each other once throughout the year, ahead of a playoff series that would see the top Northern and Southern Hemisphere sides meeting in a final at a neutral venue in Europe.

For Japan, that would mean hosting the likes of New Zealand and South Africa in July — when temperatures last year topped 40 C — and potentially moving the Top League season to earlier in the year.

A January to May season, however, would be problematic, not least because the universities, who provide all the domestic players, run their programs from April to March in line with the academic year.

France has no such worries regarding timing, but Michalak warned about the danger of year-round rugby.

"We want to create more opportunities to play international rugby because the more games countries play at international level, the better they become, and the better it is for world rugby," he said.

"As we have seen with Japan's involvement in Super Rugby, it will see the players improve, so it is a great opportunity for the players. "But as we have seen in France, if the players get too tired because the season is too long, they can't progress and things get hectic."

The proposed tournament would not run in a Rugby World Cup year, and the two players — who faced each other in RWC 2003 in Townsville, Australia, when France won 51-29 — pointed out how their nations were approaching this year's event in Japan in differing styles.

While Japan has a virtually empty calendar — save for the Sunwolves Super Rugby franchise and the Pacific Nations Cup — leading into the opening game in Tokyo on Sept. 20, it will be business as usual for the French players with Six Nations, European Cup, and domestic league games.

"As a Top League coach it is difficult for me to say too much," said Miuchi, who oversees the forwards at Hino Red Dolphins.

"I understand the World Cup is the priority as regards the calendar, but I think there should have been some Top League games in part to really raise awareness of rugby in the country."

Michalak said the upcoming Six Nations will give French fans a chance to see where the team is, but admitted it would be tough for the players who will "play a lot" before they head into a two-month camp in June.

Both former players spend a great deal of time coaching kids in their respective countries, and both hoped the 2019 and 2023 versions in Japan and France will help increase numbers. But both said more needed to be done outside the rugby community.

"Japan's win over South Africa in 2015 saw a rise in player numbers but it was only temporary," said Miuchi.

"We need to make those increases permanent, and one way to do that is to get the education system to encompass the spirit of rugby in terms of things such as teamwork and camaraderie."

Michalak said he hoped France's Ministry of National Education would have more dealings with rugby and other sports, as he believed many positive changes could come from the bottom up, including preventing injuries, which have started to blight the sport.

"We need to teach the right techniques at school regarding tackling, such as where to put your head and shoulders, as I think that is the best way to prevent injury," he said, adding that players know it is a physical sport and expect to be injured in their career.