Mark Webber could yet have an important role to play in Sunday's Brazilian Grand Prix after topping first practice.

The Australian is no longer in title contention after failing to score in the last five races, but his presence could prove vital to Red Bull Racing team-mate Sebastian Vettel.

The 22-year-old German trails championship leader Jenson Button by 16 points with two grands prix remaining and ideally needs another victory to follow on from his triumph in Japan 12 days ago to keep him in the hunt.

With Button also fighting Brawn GP team-mate Rubens Barrichello, who is 14 points adrift, Webber could be in a position to come to Vettel's aid should the team ask for his assistance.

The 33-year-old was certainly on the pace throughout the entire 90-minute session around the undulating Interlagos circuit, closing out with a lap of one minute 12.463 seconds.

Webber finished 0.411secs quicker than Barrichello, with Vettel third quickest and Button seventh, the latter 0.678secs down.

Brackley's Brawn GP team CEO Nick Fry declared himself happy with Button's work as the team focused on aerodynamics, notably to the front wing.

The McLaren duo of Heikki Kovalainen and Lewis Hamilton suggested they will be in the mix this weekend as they were fourth and fifth in a session that was hit by two rain showers.

Both were just over half a second off Webber, with Grove-based Williams' Kazuki Nakajima sixth, narrowly ahead of Button who set his best time of 1:13.141 with the last of his 29 laps.

Nico Rosberg in his Williams, Silverstone-based Force India's Adrian Sutil and Kimi Raikkonen for Ferrari completed the top ten, followed by Toyota's Jarno Trulli and Nick Heidfeld in his BMW Sauber.