Valtteri Bottas headed Max Verstappen and Lewis Hamilton in a tight first practice at the Spanish Grand Prix.
Bottas in the Mercedes was just 0.033 seconds quicker than Verstappen's Red Bull, with Lewis Hamilton 0.123secs behind his Finnish team-mate.
McLaren's Lando Norris was fourth quickest, ahead of the Ferraris of Charles Leclerc and Carlos Sainz.
Alpha Tauri's Pierre Gasly was seventh, ahead of Sebastian Vettel's Aston Martin.
The session followed the pattern of the season so far at the front, the Mercedes and Red Bull cars extremely closely matched, and McLaren and Ferrari their closest challengers.
Ferrari's pace was notable for coming on the medium tyre, while almost all the other drivers set their fastest time on the faster soft, which the Italian team did not use.
Norris was just 0.440secs off the pace in the McLaren, as he tried a new front wing and floor for the team's first big upgrade of the season.
Leclerc was only 0.052secs off Norris, with team-mate Sainz just 0.024secs further back.
Red Bull's Sergio Perez was ninth fastest after a difficult session, lacking pace and then suffering traffic problems on what might have been his fastest lap at the end of the session.
Vettel's team-mate Lance Stroll completed the top 10.
The Alpine team, fresh from a strong performance in Portugal last weekend, were only 12th and 15th fastest, with Esteban Ocon ahead of Fernando Alonso.
However, Alonso in particular ran the session in a different way, using the soft tyre when the track was 'green' and slippery early in the session and then switching to the hard for the rest of the hour.
Two drivers went off. Nikita Mazepin spun his Haas on his first flying lap, while Alfa Romeo reserve Robert Kubica lost his car through the reprofiled Turn 10 midway through the session and brought it to a brief halt while the car was recovered.
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