The 63-year-old, who took charge last month from Vahid Halilhodzic, attempted to take the pressure off his players ahead of their warm-up game with Ghana in Yokohama on Wednesday.
"The final 23 players won't be decided by one game," Nishino said.
"At this stage of course I have a general idea but I have to plan for what happens in the case of injuries," added the former Japan Football Association technical director, who names his squad for Russia on Thursday.
"Right up until the morning after the Ghana game, I have to think about all sorts of eventualities - I'm sure the doubt and anguish will continue."
Japan meet Colombia, Senegal and Poland in Group H and Nishino wants talismanic forward Keisuke Honda and playmaker Shinji Kagawa to take a key role.
Leicester City striker Shinji Okazaki will, like Kagawa, be given every chance to recover in time for the FIFA World Cup as Nishino looks to have a strong Japanese squad in Russia.
"It goes without saying that it's a survival situation for the players," said Nishino, referring to fringe members and those carrying knocks. "But first we have to focus on the Ghana game."
Japan, who will be playing in their sixth successive FIFA World Cup, have twice reached the last 16 -- in 2010 and as co-hosts in 2002.
Source: AFP
