Robert Kubica set the quickest time during 2020 Formula One pre-season testing on Wednesday at the Circuit de Barcelona-Catalunya.
He topped the timesheet in his Alfa Romeo with a fastest lap of one minute, 16.942 seconds.
Max Verstappen went second-fastest for Red Bull during his 83 laps, ending 0.405 seconds behind Kubica's quickest run.
Windy conditions provided complicated driving conditions, but AlphaTauri's Pierre Gasly and Alexander Albon of Red Bull gave eye-catching runs during the morning.
World champion Lewis Hamilton was seventh-fastest overall, and Mercedes completed 179 laps during a productive day as they tested their new steering design.
Here's Wednesday's classification:
It was a cool morning in Barcelona so maintaining tyre temperature was vital, as Kubica discovered just over an hour into the session:
He wasn't the only driver to encounter difficulties in the early running.
Ferrari's Sebastian Vettel took a trip into the gravel, while Nicholas Latifi had an issue with his Williams:
After some early duelling between Hamilton and Vettel atop the timesheet, Lance Stroll of Racing Point leapfrogged the pair with a 1:17.787 on medium tyres shortly before the halfway mark.
Before long, Hamilton was back on top, but he couldn't match the time set by Kubica with less than an hour remaining in the session.
The Mercedes man did record the most laps in the morning session, though, with 88, while Vettel was close behind on 84 during 65 minutes on the track.
Ferrari ended down the timesheets, but the Italian team produced conservative efforts as they limited the pressure on their cars.
The Prancing Horse refused to show their hand, keeping their straight-line speed controlled, but Vettel and Charles Leclerc looked good through the corners.
Testing continues on Thursday, with teams slowly pushing their engines harder before the first race of the season in Australia on March 15.