Lewis Hamilton was only 11th fastest as Mercedes struggled 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.
It appeared as if the world champions were facing similar problems to Monaco, which has a similarly low-grip track surface and where they were struggling to get the tyres into their operating temperature window.
Ferrari were more competitive than they expected on a track they thought would 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.