Williams hopeful Nick Heidfeld lapped faster than Brazilian rival Antonio Pizzonia on Friday in a test that could be crucial for his Formula One future.

The German was second quickest at the Jerez circuit in southern Spain, ahead of Brazilian Rubens Barrichello's Ferrari on the timesheets with only his former Sauber team mate Kimi Raikkonen faster in a McLaren.

Heidfeld did 65 laps with a best time of one minute 16.740 seconds, compared to Pizzonia who did 148 laps with a quickest of 1:17.056.

The two are vying for the most coveted vacancy remaining in Formula One, a place alongside Australian Mark Webber at the BMW-powered team that finished fourth this year.

Pizzonia was the favourite going into the test as the incumbent test driver who raced four times this year as a stand-in for injured Ralf Schumacher.

However Heidfeld, who drove for Jordan in 2004, was impressive in wet weather testing last week and Williams asked him back for a further assessment.

The 27-year-old lost some track time on Friday, when conditions were ideal, due to a technical problem and set his fastest lap right at the end of the session.

Technical director Sam Michael said the German would have one more day in the car on Saturday in a controlled wet weather test for tyre supplier Michelin.

"Nick has done a good job for us so far," he said.