Lewis Hamilton is only 11th fastest as Mercedes struggle in second practice at the Azerbaijan Grand Prix.
Hamilton was a second off the pace-setting time of Red Bull’s Sergio Perez as both he and team-mate Valtteri Bottas struggled on the softest tyre.
Mercedes were unable to generate any lap time on the soft tyre, which will be used to define the grid on Saturday.
Hamilton’s title rival Max Verstappen was second fastest, 0.101 seconds behind team-mate Perez.
Ferrari drivers Carlos Sainz and Charles Leclerc were third and fourth, despite Leclerc having a light impact with the wall on a lap that would have put him ahead of his team-mate and possibly the Red Bulls as well.
Leclerc, whose crash in final qualifying in Monaco two weeks ago ultimately ruined his weekend when the car failed before the race as a result of the impact, misjudged Turn 15 and nosed into the barrier.
His front wing came off, but he was able to reverse out of the barrier and return to the pits with no other damage.
Alpha Tauri’s Pierre Gasly was fifth quickest, ahead of the Alpine of Fernando Alonso, Alfa Romeo’s Antonio Giovinazzi and McLaren’s Lando Norris.
Alpine’s Esteban Ocon was ninth, ahead of the second Alpha Tauri of Yuki Tsunoda.
But it was Mercedes’ lack of pace that was the standout story of the session.
Hamilton, who enters this weekend four points behind Verstappen in the championship, complained that he “didn’t know where the time was”.
Bottas had a terrible day, ending up down in 16th fastest after a number of off-track moments.
Both drivers also struggled in the first session, in which Hamilton was seventh and Bottas 10th.
Hamilton said: “I generally had a really good day. It was clean, I got all the laps we needed. There weren’t many mistakes – I had one lock-up in P1. We were just slow. I was driving well. There was just no more time in it.
“We are definitely quite a chunk down and everyone will be scratching their heads trying to figure out how we can improve.
“I was on the limit but the car is limited. There are areas I should be quicker but there was just no more grip. But we’ll work on it. It is not easy to be out of the top 10 on pace when we have had pace in other places. I don’t really know why we are where we are.”
Bottas said: “It is going to be a long night tonight. I think there is something fundamentally wrong and we have to figure out what.”
By contrast, Verstappen was happy overall with Red Bull’s day.
“We had a great start to the weekend so far,” he said. “The car in P1 felt really decent. I was quite comfortable. For P2 we made a few changes to see if it would be better and I think we went a bit backwards. We will look overnight what direction to go in but nevertheless still a very good day.”
Ferrari were expecting the Baku track to expose their straight-line speed deficit, while Norris was not as quick as he had been in the first session, when he was on a lap that would have put him fastest of all.
Leclerc said: “It is definitely better than we expected but it is only Friday. The pace looks promising. We will keep working and hopefully it will be as good tomorrow.
“I actually felt quite comfortable in the car today, especially on braking – maybe a little bit too comfortable and pushed a little too much in Turn 15. But at the end of the day that is what practice is for. I was trying a little bit the limit and I was on a good lap.
“I feel like McLaren are very quick but just haven’t showed it today. I feel like they are still bit ahead of us. I don’t know what happened with Mercedes but I am sure they will be in front.”