Leclerc laments loss of power as Ferrari struggle
The Monegasque driver, who has taken nine pole positions this season, qualified seventh behind both Red Bulls, both Mercedes, his Ferrari teammate Carlos Sainz, who was fifth, and Alfa Romeo's Valtteri Bottas.
Leclerc showed he had recovered from his crash in Friday's second practice session, but he complained of engine problems and requested a Ferrari investigation.
"We need to look at it," he said. "I've been losing quite a lot of time down the straights in qualifying ... FP3 was not great, so we need to look into it.
"We had quite a lot of problems with the engine today for some reason and I had very bad drivability in all the high-speed corners and the car was not really responding to what I was doing with the throttle.
"And then down the straights, we were so slow. So, we'll look into it."
Leclerc said he did not think his difficulties were due to the altitude of 2,200 metres at the Autodromo Hermanos Rodriguez.
He was also downbeat about his prospects for Sunday's race.
"I don't really know what I can do," Leclerc said. "For now, I need to speak with the team to see what we can do, but obviously we cannot change much so I'm not sure."
Leclerc had been the main rival to Red Bull's Max Verstappen as he raced to his second drivers' world championship.
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