McLaren's Heikki Kovalainen led a wet first free practice session at the Japanese Grand Prix today while championship leader Jenson Button was only 18th quickest.

Button can win the Formula One title with two races to spare on Sunday if he beats Brawn GP team mate Rubens Barrichello by five points.

With rain falling and dark skies over the Honda-owned circuit early in the morning, there was an unfamiliar look to the top of the timesheets.

Japan's only regular race driver Kazuki Nakajima, still without a point after 14 races, had enjoyed a rare moment in the limelight when he led for Williams until toppled by Kovalainen in the closing minutes.

Force India's Adrian Sutil was third fastest ahead of former team mate Giancarlo Fisichella in a Ferrari and Swiss rookie Sebastien Buemi for Toro Rosso.

Only Fisichella among the top five had previously raced a Formula One car at Suzuka, making its return to the calendar for the first time since 2006.

McLaren's world champion Lewis Hamilton, also making his first appearance at the track, was sixth. Barrichello, 15 points behind Button, was ninth.

Toyota's Timo Glock, second in Singapore last weekend, was unable to take part in practice after being laid low with a heavy cold and fever.

The German was replaced by Japanese reserve driver Kamui Kobayashi. He ended the session ahead of Renault's French rookie Romain Grosjean after holding up well against Toyota's Jarno Trulli for much of the session.