McLaren's Jenson Button topped free practice for the third time in a row at the Japanese Grand Prix on Saturday, relegating champion-elect Sebastian Vettel to third. The 31-year-old Briton, who led both practice sessions on Friday, recorded a lap of 1min 31.255secs 12 minutes before the end of the crash-hit, hour-long session, giving him a clean sweep of all three on-track practices. Button’s compatriot and team-mate Lewis Hamilton was second, half a second adrift, while Red Bull's Vettel was well in the hunt for the single point he needs to seal back-to-back world titles. Vettel, who was dominated the season with nine victories so far, needs only to finish 10th or higher to seize the driver's crown, which will also be his if Button fails to finish. Qualifying for Sunday's race is later on Saturday. Spain's Fernando Alonso was fourth for Ferrari, with Australian Mark Webber recovering from electrical problems early in the session to finish fifth for Red Bull. Brazilian Felipe Massa was sixth for Ferrari, with the all-German Mercedes line-up of Michael Schumacher and Nico Rosberg seventh and eighth respectively. Russian Vitaly Petrov (Renault) and German Adrian Sutil (Force India) rounded out the top 10. The hour-long session was held in glorious sunshine at Suzuka, and it was Button who fired the first salvo, going to the top of the timesheets after 18 minutes and extending his lead to nine-tenths of a second on his next lap. Rosberg deposed the Briton from top spot after 39 minutes, and six-time Suzuka winner Schumacher briefly took over at the head of the pack until Button set the quickest lap time of the weekend, a mark that was not to be troubled. A crash by Brazilian Bruno Senna halted the session after 24 minutes when the Renault driver spun after accelerating off artificial turf at the exit of the Spoon Curve at turn 14. He slewed across the circuit before nosing his car into the barriers, causing a nine-minute delay as marshals removed debris from the track. The Brazilian was unhurt in the accident, and finished the session in 17th place. The HRT of Italian Vitantonio Liuzzi also failed to make the end of the session, with Liuzzi forced to park his car at turn 15 with 25 minutes remaining with a hydraulics problem. Liuzzi completed just four laps in Friday practice with reliability issues, and managed just eight on Saturday morning before encountering more difficulties.