Sergio Perez crashed his Red Bull at the famous Parabolica corner in Friday practice at the Italian Grand Prix.
It was the latest in a series of errors by the Mexican, whose hopes of a title challenge to team-mate Max Verstappen faded earlier this year.
Ferrari's Carlos Sainz was fastest, by 0.019 seconds from McLaren's Lando Norris, with Perez third.
Verstappen's best lap was wrecked by traffic and he ended the session only fifth, behind McLaren's Oscar Piastri.
Perez's crash, from which he emerged unhurt and did only relatively light damage to his car considering the high speed at which he lost control, blotted what had otherwise been a strong day for him.
Perez was actually faster than Verstappen on the race-simulation runs in the last part of the session by about 0.1secs on average over the few laps they managed before the crash.
And he said that overall it had been a good day for him, despite the accident.
Perez said: "I understeered off on the exit and tried to keep it nailed. I thought I had it under control, but then I touched a little bit the gravel and that was game over.
"It doesn't look too bad, the damage. The hit was fairly small. I don't think we lost anything at the end.
"The positive is the car is performing well and I'm feeling comfortable with it and I think we're in a good position for the rest of the weekend, I really felt we had a very strong Friday. This has been the best Friday in a while for us."
Norris said his McLaren was flattered by his fastest lap, on the softest tyres.
"Really the only run we look competitive was this final run, which makes us look very good," Norris said, "but I would say we are not as good as it looks.
"With the medium and hard (tyres), we struggled quite a bit more and also on the race runs we struggle quite a bit more than on the one-lap soft.
"It's a C5 (the softest tyre in the range) so it is a soft tyre and provides a lot of grip for one lap which is a good thing for us, it brings the balance closer towards us. It gives us what we almost wish we had from the car itself.
"But as soon as we lose that extra grip and go to high fuel and on different tyres, our performance relative to others decreases quite a bit. I'm happy, we made some improvements but definitely still not in a competitive-enough place.
"It's clear where we're still losing, the major is on the straights compared to a few cars, the Ferrari is unbelievably quick on the straights. We expected Ferrari to be quick here, they have a good balance in slow-speed corners and are always slippery in the straights."
Verstappen, who can win a record-breaking 10th consecutive race this weekend, said he still had work to do to fine-tune the car, and his best lap was ruined by traffic, but he said: "I've no doubt we'll get there."
It was a strong day from Sainz, on his 29th birthday. He topped the second session after being second fastest, only 0.046secs behind Verstappen, in the earlier first hour.
His team-mate Charles Leclerc was sixth fastest in the second session, 0.361secs off the pace, and fourth quickest behind Perez in the first.
Williams driver Alex Albon was seventh fastest, followed by Aston Martin's Fernando Alonso, Williams driver George Russell and the Haas drivers Nico Hulkenberg and Kevin Magnussen.
Lewis Hamilton was only 17th fastest, complaining that he was lacking speed on the straights after apparently choosing a higher-downforce set-up than Russell.
The seven-time champion asked to change his car during the session but was rebuffed by his race engineer Peter Bonnington, who said it would prevent them doing the running they needed.
He said he was "hoping to get into the top 10" in qualifying, but "I don't know how easy it will be with our current pace but that's what we will work on overnight".
Alonso's team-mate Lance Stroll had a difficult day. He sat out the first session so reserve driver Felipe Drugovich could be given some mileage, and then his car broke down with a fuel-system problem on his first lap out of the pits.
It leaves the Canadian going into Saturday having done not a single flying lap.
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