And Petrov, whose Friday was punctuated by spins, blamed his struggles on adapting to the Kers energy recovery and power-boost system, of which Heidfeld has experience from his time at BMW Sauber in 2009.

BBC: Nick Heidfeld heads Fernando Alonso at his Renault test

Hamilton, 24, said the Kers (Kinetic Energy Recovery System) power-boost system - which Ferrari are also using - proved "anything can happen" and the Briton is optimistic he can replicate the pace he found in Hungary.

BBC: McLaren talk up Kers 'advantage'

Red Bull will accept that they are likely to get passed by a McLaren or Kimi Raikkonen's Ferrari, who have the benefit of the kinetic energy recovery system (Kers) power boost on the run down to the first corner.

BBC: David Coulthard column