Red Bull’s Max Verstappen was in impressive form as he set the pace in second practice at the Azerbaijan Grand Prix.
The Dutchman, who topped both practice sessions on Friday, was 0.1 seconds quicker than Mercedes’ Valtteri Bottas.
Ferrari’s Kimi Raikkonen and Sebastian Vettel were fourth and fifth, with Mercedes’ Lewis Hamilton only 10th.
Renault’s Jolyon Palmer crashed at Turn Eight, causing a stoppage for 15 minutes while the car was cleared.
The accident will heap further pressure on the Englishman, who is in danger of losing his drive in mid-season because of his poor form compared to team-mate Nico Hulkenberg.
Renault are set to replace Palmer after the Hungarian Grand Prix at the end of July if his form does not improve, with reserve driver Sergey Sirotkin the current favourite to take the seat.
Friday’s incident followed a prickly interview between Palmer and BBC reporter Jennie Gow at the pre-event media day on Thursday.
Renault’s Cyril Abiteboul said: “We are committed to helping him through this tough period. He has no ultimatum but at the same time he has to deliver.”
A Red Bull fastest? What’s going on?
After Verstappen set the pace in first practice, team boss Christian Horner said he did not expect Red Bull could keep that position as Mercedes and Ferrari upped the pace in second practice.
But the Dutchman’s impressive form continued. He was the man to beat throughout the session, setting the pace on both the soft and super-soft tyres.
If Red Bull can keep up their form into the weekend, it would be a major surprise, as they have lagged at least 0.5secs off Mercedes and Ferrari for most of the year.
Baku is a track that should expose the power deficit of the Renault compared to the Mercedes and Ferrari, although this will have been reduced by a Renault upgrade that managing director Abiteboul said was worth 0.2secs a lap.
But even Verstappen became a victim of the low-grip surface and problems keeping the tyres in their operating window – he was one of many drivers to miss their braking point and run into an escape road, in his case at Turn Two.
And he had a late crash, swerving into the barriers at Turn One with a minute to go and damaging both right-hand wheels and suspension and the front and rear wings.
His team-mate Daniel Ricciardo was third fastest, just 0.111secs slower, increasing the impression Red Bull are in an unexpectedly competitive position this weekend.
Raikkonen was only 0.127secs off the pace in fourth and 0.126secs quicker than Vettel.
Williams rookie Lance Stroll was an impressive sixth quickest, two weeks after scoring his first points at his home race in Canada. Team-mate Felipe Massa was 11th after not setting a time on the super-soft tyre.
Another difficult weekend for Hamilton?
Hamilton had a particularly difficult day, failing to get in a quick time on the super-soft tyre – just as he did in the first session – and ending up 1.163secs off the pace.
The track was difficult for everyone – Vettel, Fernando Alonso and Felipe Massa were among the other drivers to visit the escape roads.
But it is not the first time Hamilton has struggled to put a lap together on this kind of low-grip street circuit with big braking zones into right right-angled corners.
It is early in the weekend to draw too many conclusions but at this stage the weekend in Baku has worrying echoes of his races in Russia in April and Singapore last year, when Hamilton had similarly messy weekends and was never in the game. Monaco this year was similarly difficult for him.
“I’m definitely still in the fight for pole, but it is definitely difficult,” Hamilton said. “There is a small window that the tyres work in and at this track it seemed the most difficult.
“We know the potential of the car but it is easy be out of the window and not extract it. When you have that there are lots of question marks and only a certain amount of time to answer all of them.”
Vettel, by contrast, had a solid day. The German, 12 points ahead of Hamilton in the championship, ended up fifth quickest on absolute times, but was very fast on the race-simulation runs later in the session.
Vettel was quickest, but there was little to choose between him, Bottas and Verstappen.
Mercedes boss Toto Wolff said: “Baku is a tricky one because you have to get into the rhythm to gain confidence and heat the tyres properly so they generate grip so you need problem-free runs, little traffic, no yellow flags and he had all that so it was difficult to be quick.
“Most of the cars had problems today. There were many lock-ups and spins, so the track is tricky for all teams and drivers, but being in the right position on the track at the right time is difficult and we weren’t the best today on that.”
More McLaren woe
McLaren entered the weekend knowing that Alonso and team-mate Stoffel Vandoorne would be starting from the back because of penalties for using excessive numbers of engine parts.
But the weekend got off to a bad start when Alonso broke down in the middle of second practice, pulling off after Turn 15 with smoke coming from the back of the car.
The penalties arose from Honda fitting an upgraded MGU-H/turbo for the weekend. The Japanese company was also trying development parts in the engine on Friday.
Alonso had said “engine, engine” over the radio as he pulled off the track, but the team later said it had been a gearbox problem.