Lewis Hamilton led a Mercedes one-two in second practice at the Spanish Grand Prix as Max Verstappen failed to set a representative lap time.
Hamilton was 0.139 seconds faster than team-mate Valtteri Bottas, with Ferrari's Charles Leclerc in third.
Verstappen made an error on his qualifying simulation run on the soft tyres and ended ninth with a time set on medium tyres earlier in the session.
The Alpines of Esteban Ocon and Fernando Alonso were fourth and fifth.
Alpha Tauri's Pierre Gasly and Yuki Tsunoda were next up, ahead of the second Ferrari of Carlos Sainz, and the two Red Bulls of Verstappen and Sergio Perez.
McLaren have not so far shown the pace that has put Lando Norris third in the championship after three races and the Briton was 12th with team-mate Daniel Ricciardo down in 15th.
Verstappen had a difficult day with track limits - not for the first time this season.
Verstappen appeared to have the pace to challenge Mercedes closely, as has been the case so far this season - he was about 0.1secs off Hamilton's time two-thirds of the way around the lap before trying to carry too much speed through Turn 10.
He ran wide off the track and then almost lost the rear and had to back off, and was unable to record a second lap on the fragile tyres.
As well as the moment on his qualifying simulation lap, he ran wide at Turn Seven in both sessions, damaging his front wing each time over the new kerbs that have been inserted on the exit to restrain the cars.
Perez, though, was struggling for one-lap pace. He did get a lap on the soft tyres but was just over 0.1secs off Verstappen's medium time and the Mexican looked to be struggling to find the limit of the car so far at the Circuit de Barcelona-Catalunya.
When the drivers simulated race running at the end of the session, the Mercedes drivers had 0.4secs advantage on average pace over Verstappen on the soft tyre, while the Red Bull managed only one lap on the medium tyre which made it difficult to compare the two cars on that rubber.
Of the teams battling just behind the front-runners, Leclerc and Alonso were the two fastest cars on average on the soft tyre.
Earlier in the day, Bottas had led the first session, with Verstappen splitting him from Hamilton, and just 0.123secs separating the three.
Hamilton said: "It's been a good start to the weekend. Track's awesome and balance similar to the last race so it looks close but it looks like we've got decent pace today."
Verstappen, who is eight points behind Hamilton in the championship, said: "A little bit wide in Turn 10 but overall we had quite a good day.
"The car seems quite competitive so I am looking forward to tomorrow to try to improve a bit further. We are quite happy. You always want to improve but there was nothing weird going on today."
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