Briscoe has a 25-point lead over Dario Franchitti and could clinch his first series championship with a first or second-place finish in Saturday's race at the 1.5 mile Twin Ring Motegi oval.
The 27-year-old Australian has three victories this season for Team Penske. His chances for the title here will also depend on where Target Chip Ganassi teammates Franchitti and Scott Dixon finish.
Dixon, who is third in the standings, has never won here but the 2008 champion finished third last year and fourth in 2007.
"Ideally, we need to come home in front of them, have a good race and take as many points as possible," Briscoe said Thursday. "You have to keep an eye on them to know how aggressive you have to be."
Patrick became the first woman to win a major open-wheel event in last year's Indy Japan, winning on fuel strategy in her 50th career start. She took the lead from Helio Castroneves on the 198th lap and finished 5.8594 seconds ahead.
"It's really nice to come back to a track as the winner," said Patrick, who is winless this season. "I feel a little more confident and hopefully I can do it again."
Patrick is fifth in the standings and is not in contention for the series championship. Some criticized her fuel strategy win here last year but Patrick said that's not fair.
"Obviously, I think that's unfair," said Patrick. "Any race you go to, you have to be running well to win. There have been a lot of people who have won on strategy, strategy is a huge part of it."
The IndyCar series will compete in Japan for the seventh consecutive year. This is the first time the race, previously run in April, will factor into the championship.
Practice and qualifying will be held on Friday.