Ferrari F1 qualifying slump "interesting" - Mercedes' Allison

Red Bull driver Max Verstappen has qualified on pole for the Brazilian GP, two weeks after Mercedes' Valtteri Bottas topped qualifying in the United States.

Ferrari had started the previous six grands prix from pole position, although it was only fastest in five of those as its most recent pole came after poleman Verstappen picked up a grid penalty in Mexico.

The FIA has recently issued two technical directives to stop teams potentially exploiting oil burning and fuel flow regulations for performance gains.

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Verstappen has led suggestions that the FIA's decrees have triggered Ferrari's lost qualifying edge, rather than simply coinciding with it.

Ferrari had a strong Friday at Interlagos with notably superior straightline speed, but that advantage was significantly reduced in qualifying.

Asked by Autosport for his thoughts on Ferrari's change in straightline speed gains in Brazil, Allison warned against making assumptions but admitted the shift in form was noteworthy.

"I think they were still pretty useful on the straights," said Allison. "But not quite as marked as it was [on Friday].

"That could be all sorts of things. We all run different power modes on a Friday.

"Probably the only thing that you could stand back from a distance and say is that it's two races on the trot where it hasn't been pole position for a Ferrari. And they sort of had a reasonably comfortable margin [before that].

"So it's an interesting thing, but not anything you could draw any solid conclusions from.

"They're still a quick car on the straights and let's just see how they are in the race, how they are in the in the races to come."

Verstappen outqualified the lead Ferrari of Sebastian Vettel by just over a tenth of a second at Interlagos, where the Red Bull was fastest in the twisty middle sector.

Ferrari's Charles Leclerc narrowly topped the speed trap figures and held a bigger 3.5mph advantage over Verstappen at the finish line, but was only 1.4mph faster than the best Mercedes.

Leclerc also set the fastest time in sector three, which comprises the Juncao left-hander and then a flat-out blast lasting more than a kilometre to the finish line, but both Mercedes and Red Bulls were within a tenth of him there.

Asked if he was surprised by the performance of Verstappen and Red Bull, Allison said: "I'd clearly prefer it if it was us that was on pole.

"But Max has looked quick all weekend and it's not the first time this year that Max has been the quickest car.

"So it would be wrong to say this is a complete bolt from the blue.

"That's a very good car and an extremely good driver so they did a better job than we did and deserved pole position."