After 10 races, the Mexican was second overall but 99 points behind his dominant teammate and two-time world champion Max Verstappen when he hit the tire wall at turn five.
“I can’t believe it,” Perez told team radio, the wrecked car appearing to have sustained heavy damage.
“I cut the grass, I think about the braking, I just lost it,” he added.
The Mexican has failed to qualify in the top ten in four of his previous five races, with just one podium in that span, and needs a great weekend with Red Bull reserve Daniel Ricciardo more in the mix as a possible replacement.
Perez was forced to skip the rest of the session as the car was towed to the pits on a truck for mechanics to begin what could be major repairs.
“It’s obviously frustrating…hopefully it (the damage) is mostly limited to the front right corner, which hopefully will be repairable in time for the next session,” team boss Christian Horner said.
“It was unfortunate, he just put a wheel in the grass and made a mistake in turn five.
“I hope he won’t lose too much in this session because in these conditions people don’t do a lot of laps. But obviously it’s not an ideal way to start the weekend.”
Mercedes’ George Russell, who claimed his first career pole position in Hungary last year, finished first overall with a lap time of 1:38.795 seconds.
During the stop, the rain started to fall and got heavier.
Australia’s Oscar Piastri was second for McLaren, with Aston Martin’s Lance Stroll third and McLaren’s Lando Norris fourth.
Seven drivers, including Verstappen and Ricciardo, failed to set a time.
One of the seven was Mercedes’ seven-time world champion Lewis Hamilton, who won a record eight times in Hungary. The Briton got out of his car before the end of the session, knowing that he had nothing to gain by being on the track in these conditions.
With 14 minutes remaining, Ferrari’s Carlos Sainz also pulled out the red flags after his car crashed onto a kerb at the third corner.
(With contributions from Reuters)
