Australian Formula One driver Mark Webber said he is not concerned by the pace of his Red Bull car, despite a disappointing performance during Friday's second practice for Sunday's Belgian Grand Prix.

Championship leader Webber wound up seventh and 18th fastest in the two opening practice sessions at the rain-affected Spa-Francorchamps circuit in Belgium.

In spite of this, the Australian insisted the results would have no bearing on his performance over the rest of the weekend.

"Today was a bit of a messy day and we are not going to lose any sleep over it," Webber told ABC Network on Saturday.

"It was actually a pretty good day, we did some good stuff and we are looking forward to tomorrow."

Webber insisted that he was not fazed by the performance of his rivals, despite Fernando Alonso of Ferrari dominating both sessions, and said that the variable weather conditions made it impossible to gauge anyone else's performance.

"I think there are a few quick guys out there, but we are not exactly slow either," he said.

"It looks like an interesting weekend, it is always changing a lot here with weather conditions and it's hard to get a feel on what anyone is doing."

The drivers will need to draw upon all their skill and experience to take on the highly challenging Spa-Francorchamps track. Nestled within the mountainous Ardennes terrain in Belgium, the circuit is known to harbor tricky weather conditions.