Charles Leclerc has conceded to fears his Mexico City Grand Prix weekend could become a "nightmare" should Ferrari be unable to solve his "strange" engine problems.
The Monégasque endured a difficult afternoon at the Autodromo Hermanos Rodriguez, qualifying only seventh fastest, behind Valtteri Bottas' Alfa Romeo and 0.780secs slower than polesitter Max Verstappen.
Leclerc's preparations for the weekend were blighted by a crash during the FP2 Pirelli tyre test, in which the rear of the car was ripped apart when hitting the barriers in the mid-sector esses.
Addressing his qualifying issues, Leclerc said: "Whether it is because of the crash, I am not sure personally.
"But speaking about this qualifying, there was something strange or wrong with the engine.
"We were losing quite a lot of time down the straights from FP3 to Q3, not compared to the Red Bull or Mercedes because this has been the case since FP1 and we knew it, but there was something strange.
"Also, the throttle, the engine was not responding to the throttle input I was having in the high speeds.
"I really hope we can fix those issues for tomorrow otherwise it will be an extremely difficult race to be consistent."
On his prospects for the race, with the long run down to turn one providing an opportunity to make an instant impact, Leclerc conceded: "If I still have the same issues, the race will be a nightmare so I hope we can fix that.
"The most difficult qualifying [of the year] by far but let's see tomorrow."