The Blue Samurai booked their position in Russia with a 2-0 win over the Socceroos in Saitama on Thursday, meaning Wednesday's (AEST) game in Jeddah is a dead rubber for Vahid Halilhodzic's men.
But the same match holds the key to Australia's qualification path, with the green-and-gold needing three points against Thailand on Tuesday before hoping Japan win or draw in Saudi Arabia.
A favourable result for the Socceroos looks to be against the odds however, with Japanese defender Maya Yoshida suggesting an experimental team is likely to be selected in the Middle East.
"I think [Halilhodzic] will try to test some different players, but the manager really is a bit of a weirdo," the Southampton centre-half said.
"Sometimes he makes decisions we don't expect, so I can't say anything."
This means the likes of Keisuke Honda, Shinji Kagawa and Shinji Okazaki may feature after failing to start against Australia.
Russia will be Japan's sixth-consecutive World Cup finals appearance after qualifying for their first at France 1998.