The F1 paddock is scratching its head about the strange and sudden decline of Ferrari's 2018 championship assault.

Some think Sebastian Vettel's struggle is because the FIA installed a second sensor in his car's controversial battery layout.

Asked if he could explain what the sensor is for, F1 race director Charlie Whiting answered: "No.

"If I did that, I would have to describe Ferrari's car and then the rest of the teams will understand some more things about it.

"I can't let that happen."

Mercedes' Lewis Hamilton, now commandingly leading the championship after Suzuka, isn't sure why Ferrari has dropped off.

"I didn't expect it," he said.

"Until the mid part of the season they were very strong and then we got to Monza where they were still quite strong, but then Singapore was where it really started to tail off.

"I don't really have an answer for that," added Hamilton. "You should ask Sebastian."

An editorial in Corriere della Sera, an Italian newspaper, links Ferrari's performance drop with the death in July of Sergio Marchionne.

Correspondent Daniele Sparisci said the former president was the "custodian of internal balance", and in the absence of that, Ferrari has split into two warring factions.

On one side, reportedly, is team boss Maurizio Arrivabene, and on the other is Mattia Binotto, who is regarded as second in line for the throne.

"It is said that relations between them is at a historic low," said Sparisci.