Sebastian Vettel was at a loss to explain his struggles in a wet qualifying for the Italian Grand Prix after slumping to eighth.

The German failed to deliver a competitive lap in Q3 and was forced to settle for P8, though he will start from sixth given Red Bull's hefty engine penalties.

Vettel admitted after qualifying that he was shocked by the pace of his rivals, with Ferrari left to investigate the cause of their woes.

"I’m that surprised by how quick the others went," the championship leader said. "So, clearly we couldn’t go the same pace.

"At this stage we don’t know why. I’m sure there are a couple of things we will look into and try understand."

In stark contrast to Saturday's washout, the race is expected to bring clear skies and warm temperatures.

Vettel, then, is confident of gaining ground as he looks to protect a slender championship lead over pole-sitter Lewis Hamilton.

"We have a good car so we don’t need to be afraid," he said.

"Obviously today didn’t go the way we wanted but for tomorrow I think we can make up a lot of ground, the car is quick.

"We know that. You can overtake here so it should be a fun race."

Kimi Raikkonen will line up one place ahead of his team-mate in fifth but was left bemoaning a total lack of grip.

"We're not fast enough," he conceded. "Obviously – at least for my car, I don’t know about the other car – I struggled a lot with the grip.

"Either we didn’t make the tyres work or whatever it is, it was worst for grip.

"Especially with this low downforce you cannot put a lot of load into the tyres and then it’s the never ending story."