Hamilton has won twice before in Suzuka, in 2014 and 2015, and was runner-up to former Mercedes teammate Nico Rosberg in last year's race. A win in Suzuka would move Hamilton a step closer to a third F1 title in four years with Mercedes and his fourth overall.
Mercedes was slower than Ferrari and Red Bull for the second straight race in Malaysia after similarly struggling for pace in Singapore. "We're still leading the championship, we've still got a great car," Hamilton said Thursday. "Each race is just really trying to understand more about the car because there's constantly something new thrown in the mix, (that) can catch us off guard."
Mercedes was debating whether to run the team's latest aerodynamic package for the Japanese GP. "After Malaysia, we have found ourselves analyzing our problems, beginning to understand their causes and working on solutions," Mercedes head of motorsport Toto Wolff said.
"While we work to improve in those areas, we must not forget the many strengths we have shown this season," Wolff added. "Our car has taken more pole positions and race wins than any other and we lead both championships."
Vettel, who had a new engine for the race in Malaysia, is a four-time winner in Japan. Red Bull driver Max Verstappen, who overtook Hamilton with ease early on to win the race in Malaysia, is sixth in the standings and will be looking to build on his momentum in Japan.
"Suzuka will always be a special place for me because I made my Formula One debut there," Verstappen said. "It's a proper old-school track."