Red Bull Motorsport Advisor Helmut Marko believes there is "no other explanation" for Ferrari's strong Mexico City Grand Prix qualifying pace than the Scuderia running its power units at full power.
Polesitter Charles Leclerc is joined on the front row by teammate Carlos Sainz after an enthralling qualifying session at the Autodromo Hermanos Rodriguez, where Ferrari's pace was only demonstrated in the final throes.
Max Verstappen had looked the driver to beat all the way through the weekend until Q3 and the Dutchman will now start third.
Teams will likely run power units below maximum performance for the event given the high altitude of the circuit, which means less oxygen for the engines to take advantage of.
But speaking to Sky Germany about Ferrari's performance, Marko said: "They must have driven at full power. It has to be.
"We have no other explanation, but that won't get you far in the race."
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Untidy Verstappen qualifying
Verstappen's qualifying was far from straightforward and the triple World Champion was investigated for a rules breach when alleged to have impeded rivals in the pit lane.
He was later cleared and will remain third on the grid but asked why he was not on pole, Marko explained: "Max did not have a clean lap in both Q3 attempts, with things going wrong in Turns 13 and 14. There he lost about one-and-a-half-tenths twice.
"With an optimal lap, we would have taken pole. However, you can overtake here, so we are still positive for the race."