Rosberg unsure about Mercedes form

"We're still a little bit down on the performance and we just need to try and extract the maximum from the car", the German driver told reporters on Friday.

Rosberg, who is eighth in the drivers' championship standings and 80 points behind leader Lewis Hamilton, said the team was focusing on racing Williams and Renault this weekend.

"If we beat the Williams, which seem to be our main competitors here, then we're doing OK," Rosberg told AUTOSPORT. "Kubica, too - that will be a close fight between us. We'll try to see if we can get ahead of them."

Both Rosberg and his veteran team-mate Michael Schumacher said they were experiencing problems with the car in Friday's second free practise, where Rosberg placed 10th and Schumacher 14th.

Rosberg "struggled a little with understeer on the faster corners", while Schumacher observed that there was still a lot of preparation to do before qualifying.

"We're using the F-duct [in testing], we're working with different things, all of equal importance", the former Ferrari favourite told reporters.

And Schumacher, who last raced before the tifosi in 2006, said he had fond memories of competing at Monza for Ferrari.

"The memories are still there, of course", he said. "After so many good years and the times we had together you feel that there is a very intense relationship - at least as I'm not fighting the Ferraris in the championship. All the tifosi are very good here."