Japan head coach Jamie Joseph on Friday named a mammoth 52-man preliminary squad to face New Zealand, England and France, saying he needs "more depth" for next year's Rugby World Cup.
Japan face the All Blacks in Tokyo on October 29 before heading to Europe to take on England at Twickenham and France in Toulouse in November.
The 2019 World Cup hosts recently ran France close in two Test matches on home soil but Joseph said he needs to "prepare more players" to deal with the demands of top-level rugby.
"We don't have a lot of depth and we've got a pandemic that we need to deal with," said Joseph, who intends to trim the squad before they play the All Blacks.
"What that means is that at any given moment we could lose players and we've got to have enough players to step up and play Test matches at the drop of a hat."
Joseph named 28 forwards and 24 backs for the team's training camp, including winger Kotaro Matsushima, who has returned to Japan's domestic league after a stint in France with Clermont.
Loose forward Kazuki Himeno also returns after missing the two-Test series against Uruguay and France in June and July through injury.
Joseph will prepare for the three Test matches by picking a Japan A team for three home games against Australia A in October.
He said coaching such a big group was "not as easy as it sounds".
"Having 50 players, we've got to bring them up to speed in how we want to play the game," said the New Zealand-born Joseph.
"That's going to take a little bit of time and it's also going to take a bit of planning."
Joseph said his team's two wins over Uruguay and two losses to France were "a fair reflection" of where they stand.
Japan led France until the 71st minute in the second Test in Tokyo but ended up losing 20-15.
Japan have been drawn with Chile, England, Samoa and Argentina in next year's World Cup in France.