Heidfeld delighted with first day back

The German, replacing Pedro de la Rosa at the Sauber team, was quickly up to speed and was able to match the pace of his team-mate Kamui Kobayashi.

Heidfeld finished the day in 13th position, just over a tenth behind Kobayashi.

Heidfeld, who had not driven in a grand prix since last year, believes there is still more to come.

"Given it was my first day back in the team and also in the 2010 car I'm very happy," said Heidfeld. "I enjoyed driving a lot. At the beginning it was a bit difficult because the track was wet. I just took it easy and tried to do as many laps as possible.

"For the second session we changed a few things, but it is clear two sessions are not enough to analyse everything. I see many areas where we can improve the set-up of the car and areas where I can improve in getting the best out of the car.

"The track itself with regard to the bumps has improved compared to 2009."