Mercedes driver Nico Rosberg is wary that he faces a 'tough' Italian Grand Prix after qualifying behind team-mate Lewis Hamilton and both Ferrari drivers at Monza.
Mercedes detected a problem with Rosberg's upgraded power unit prior to qualifying and the outfit was forced to re-install an old unit, which has already completed six races.
With Rosberg using an old non-upgraded specification engine, he could manage only fourth place and isn't confident that matters will improve in the race.
"With every kilometre you lose a bit of power and Monza is a power track where the engine has a big impact," he said.
"It will be tough tomorrow, as I will probably also be a bit slower in the race because of that. But I will never give up.
"I have to fight for a great start and hope to overtake the two Ferraris in front of me quickly to give myself a chance of catching Lewis."
Hamilton collected his 11th pole position of the year but is aware that he will have to defend from both Ferrari drivers on the run down to the Rettifilo chicane.
"Ferrari did a great job," he said. "They're very close here and it'll be a good fight. In terms of my lap, it was good but not perfect. My Spa qualifying lap was definitely better.
"Pole is always a great feeling but there's a long way down to turn one and Ferrari are strong off the line. Last year I didn't have a good start and had to fight hard so nothing is done yet.
"We've shown strong pace in our long run simulations though so hopefully we can keep that up tomorrow in the race."