Red Bull's Mark Webber was fastest in Saturday's final practice for the Japanese Grand Prix after world champion team mate Sebastian Vettel was sidelined by a KERS battery problem.
Vettel, who can secure his fourth successive Formula One title in Sunday's race if he wins and Ferrari's Fernando Alonso fails to finish in the top eight, ended the session with the ninth quickest time.
However the 26-year-old German, who has qualified on pole position in Japan for the past four years and has also won three of the last four races at Suzuka, managed only eight laps compared to Webber's 17.
Vettel was changed into a jeans and T-shirt before the end of the session, watching in the garage for the final 15 minutes as mechanics changed the battery on his car's KERS energy recovery system.
Webber's time of one minute 32.053 seconds was 0.134 faster than Lewis Hamilton in the Mercedes with the Briton's team mate Nico Rosberg third fastest.
Alonso, who is second overall in the title race but 77 points adrift of Vettel, was fifth fastest with the main battle in qualifying looking likely to be between Red Bull and Mercedes.
Adrian Sutil crashed his Force India at the exit to the Spoon Curve, spinning and hitting the barriers.