With less than a year until the 2019 Rugby World Cup, Japan coach Jamie Joseph says his team needs to develop depth in key positions if they are to fulfill their ambition of reaching the last eight.

Speaking prior to the launch Thursday of events in Japan to mark one year to go before the Brave Blossoms kick off the 2019 World Cup in Tokyo on Sept. 20, 2019, the 48-year-old New Zealander said he is "trying to grow depth in every position, because if we get an injury...it leaves us vulnerable."

(Japan players celebrate after a surprise 34-32 victory over South Africa at the 2015 Rugby World Cup in England)

"One of our weaknesses is we don't have a lot of depth. That's always been a challenge for Japanese rugby. Our top 20 players are good enough, (but) our second 20, through lack of experience or opportunity in Top League, don't have other competitions to improve and just haven't had enough time to get used to international rugby."

Joseph, who played for the All Blacks at the 1995 World Cup and for Japan four years later, said he is trying to give players opportunities at the highest level, but it is tough given he also has to win test matches to appease the public and media.

Flyhalf and scrumhalf are a particular issue outside the top-line players, he said, and that can put Japan under pressure.

However, he said he is pleased players are becoming a lot more proactive, that they are more willing to try new things rather than waiting to be told what to do and worrying about making mistakes.

"Having been here two years, I think we are progressing well. We have got new players that have established themselves as international players for Japan. Players such as (Kazuki) Himeno, Koo (Ji Won), (Kenki) Fukuoka and (Yutaka) Nagare."

"They have shown that they can compete at this level and compete very well. And as a team the players understand our game plan now and are, therefore, playing better and are a lot more confident against some of the tough teams."

But he said players still make simple mental mistakes that cost the team test matches, and if repeated in 2019, will prevent Japan from reaching the quarterfinals on home turf.

"We have to be smarter and work harder (than other teams). But that is the strength of Japanese players. They are willing to work hard as long as they understand why and how it will help us win."

"We have to play a type of rugby that is very easy to watch and very easy to understand, that the players are totally committed to. The players need to be smart, understand the game plan and execute it to the very best. If they do that I am confident we can do very well."

And he believes that work ethic will also ensure the Japanese public will buy into what the Brave Blossoms are trying to achieve.

"For all non-rugby people in Japan, they are going to know what rugby is all about and that's great for our game. You don't have to be a rugby fan to cheer for Japan. You don't even have to like sport. We are going to have everyone here rooting for us and that's good for our sport."

With the start of the 2019-2020 Top League season pushed back to January 2020, Joseph will have his team for nine months prior to the World Cup. And he intends to put the time to good use.

"Next year we just need to polish what we are doing. There is nothing secret about it, just a lot of hard work and a lot of belief which leads to confidence when you go out and play the game."