Australian Jack Miller produced the best time in Friday's practice at the European MotoGP in Valencia, while championship rivals Joan Mir and Fabio Quartararo cracked the top 10 despite struggling in a wet opening session.
After dominating on a slick track in the morning practice, Ducati rider Miller set a fastest lap of 1min 32.528sec as the Ricardo Tormo circuit dried in the afternoon session.
Aleix Espargaro was a surprise second ahead of Franco Morbidelli, Quartararo's Yamaha-SRT team-mate and the Teruel Grand Prix winner from two weeks ago.
Quartararo bounced back to finish ninth in the second session having come 21st and last earlier in the day. Mir, who leads the MotoGP standings by 14 points, was 10th with both riders over 0.8sec behind Miller.
South African Brad Binder, seventh on Friday, will serve a long lap penalty in Sunday's race as punishment for the KTM rider's collision with Miller in the previous grand prix.
Quartararo, who faded badly after starting two of the past three races on pole, showed his frustration by banging his fist on his fuel tank after sliding off the track in soggy morning conditions.
But the French rider, who has won three races this season, moved up the timesheets as the weather improved for the second session.
Mir had initially fared little better than Quartararo in the first run out when he finished 1.6 seconds adrift of Miller in 17th place.
Garrett Gerloff, deputising for Valentino Rossi, was 19th on his MotoGP debut. Seven-time champion Rossi is awaiting the results of a Covid-19 test to see if he is allowed to take part in this weekend's race.
The Valencia MotoGP will be held on the same circuit next weekend before the season finale takes place at Portimao in Portugal on November 22.
Combined fastest times from Friday's opening practice sessions at the European MotoGP in Valencia:
1. Jack Miller (AUS/Ducati-Pramac) 1:32.528, 2. Aleix Espargaro (ESP/Aprilia) at 0.092sec, 3. Franco Morbidelli (ITA/Yamaha-SRT) 0.276, 4. Takaaki Nakagami (JPN/Honda-LCR) 0.338, 5. Pol Espargaro (ESP/KTM) 0.424, 6. Alex Rins (ESP/Suzuki) 0.629, 7. Brad Binder (RSA/KTM) 0.731, 8. Andrea Dovizioso (ITA/Ducati) 0.764, 9. Fabio Quartararo (FRA/Yamaha-SRT) 0.809, 10. Joan Mir (ESP/Suzuki) 0.877