Andrea Dovizioso capitalised on improved conditions in the second session of the day to post the fastest time in practice at the Czech Republic Grand Prix on Friday.
Johann Zarco set the pace in FP1 at the Automotodrom Brno, the Monster Yamaha Tech 3 rider clocking two minutes and 5.201 seconds on a wet surface.
Zarco went in front with a minute to go in the first session and stayed there, edging out Marc Marquez by only 0.039secs, with Jorge Lorenzo third.
Dovizioso came to the fore under blue skies later in the day, posting the quickest time of both sessions with a 1:56.332, ahead of Jonas Folger, who was denied top spot by 0.398secs.
Danilo Petrucci (Octo Pramac Racing) completed the top three as the riders returned to the track to gear up for the first race since the mid-season break.
Championship leader Marc Marquez was only 10th in FP2, but did not put in a late challenge on a softer tyre.
Maverick Vinales, second in the standings, was only 11th, while Lorenzo could only set the 15th quickest time on a new-look Ducati with a radical new aerodynamic package.