Sauber's form dips once more

Heidfeld, who had recovered well from a collision with the FIA medical car in the warm-up which had damaged his race car, was on course for a point when he encountered a front brake problem. His team-mate Massa was tipped into a spin by Minardi's Mark Webber and also retired.

"I made a good start this afternoon and my car felt fine to begin with, but I think I may have had a slow puncture on the right rear on my first set of tyres as Mika Salo [who went on to finish sixth] was getting close," said Heidfeld. "I had him under control, however, and after my first stop I had no trouble keeping ahead of him.

"Then, after a while, I began to feel some really strange vibrations in the front end so I had to make an unscheduled stop and then was forced to retire. It's disappointing because I could have finished sixth today," he added.

Massa, who was suffering from worsening understeer, said: "I had a great fight with Villeneuve and Frentzen but unfortunately, after my pitstop Mark Webber tried to brake very late and put me out."