Spa-Francorchamps, Belgium - BMW-Sauber driver Nick Heidfeld on Saturday managed the fastest time in the free practise ahead of qualifying for Sunday's Belgian Formula One Grand Prix at Spa- Francorchamps.

The German clocked 1 minute 45.388 seconds for a 7.004-kilometre lap, just 0.074 seconds faster than Toyota's Jarno Trulli of Italy, with Adrian Sutil in a Force India third.

Overall leader Jenson Button in a Brawn GP had the tenth-fastest time.

Ferrari's Luca Badoer, replacing the injured Felipe Massa, again struggled, finishing second-last of all the timed drivers.

Qualifying later Saturday will determine grid positions for the race.

Button leads the championship on 72 points with his Brazilian team-mate Rubens Barrichello on 54, while the Red Bull drivers Mark Webber and Sebastian Vettel are third and fourth with 51.5 and 47 points respectively.(dpa)