Aug.2 (GMM) Despite Nick Heidfeld insisting he is "relaxed" about his future at BMW-Sauber, team boss Mario Theissen in Hungary stopped short of saying the German will be retained beyond 2008.

Theissen told the news agency AFP he will wait a few more races before determining whether or not Heidfeld, 31, has overcome the performance slump he suffered earlier this season.

In the last four races, Heidfeld has scored more points than any other driver on the grid.

"I am very confident that he has overcome the weak period, but you don't get into this within a week and you don't get out of it within a week," Theissen said on Saturday.

"So, he has to work systematically -- and he is working systematically. And I am confident he will get back to full performance and full confidence."