Webber and teammate Sebastien Vettel could only finish 11th and 13th respectively but Webber has insisted that the performance of the car will improve over the weekend.
The 36-year-old said: "We're working hard, but we're not there yet. We were a bit more competitive on the longer runs in practice today.
"We're not normally the Friday world champions, so we'll do some work now for tomorrow.
"We often find a good step ahead of qualifying."
Webber finished sixth in the Belgian Grand Prix last week.