Max Verstappen believes Red Bull's failure to take pole position for the Mexican Grand Prix was "a bit of a mystery" as Mercedes locked out the front row.
Verstappen was widely expected to take pole position, having dominated the second and third free practice sessions at the Autodromo Hermanos Rodriguez.
Valtteri Bottas claimed top spot in qualifying with a mighty first Q3 run, leading a Mercedes 1-2 from teammate Lewis Hamilton.
"I think we just were really slow and just [had] terrible grip in Q3," Verstappen told media, including RacingNews365.com.
"I think my last lap we recovered that a bit just [by] getting the tyres into a little bit [of] a better window.
"But [it's] still not to what we would have liked, and how the car has been behaving in all the practice sessions, so that's a bit of a mystery.
"But then we [will] mainly race on different tyres anyway, so I expect the balance to be good again."
Verstappen's rear wing had cracks before qualifying
Before qualifying, the TV cameras picked up the Red Bull mechanics repairing Verstappen's rear wing. Tape could also be seen on the right-hand side of the rear wing during the session.
Red Bull Team Principal Christian Horner says it was "nothing serious" and Verstappen has revealed the rear wing was cracked before qualifying.
It's the second consecutive event his rear wing has been cracked, following a similar problem two weeks ago at the Circuit of the Americas.
"They were cracked after FP3," said Verstappen. "So we had to patch them up and basically they were like new to start qualifying.
"I don't think that had anything to do with it. But, of course, we'll have a look into it again."
Video: The secrets of the Autodromo Hermanos Rodriguez circuit
Follow Rudy van Buren as he takes you on a flying lap around the Autodromo Hermanos Rodriguez, home of the F1 Mexican Grand Prix.