Doha - Defending world champion Marc Marquez shrugged off any lingering effects of shoulder surgery to set the pace in practice at the season-opening Qatar MotoGP on Friday.
The Spaniard, who has captured five of the last six world titles, shaved 0.3sec off the lap record at Losail on his Honda.
Compatriot Maverick Vinales was second fastest overall on his Yamaha with Australia's Jack Miller a surprising third on a Ducati.
Marquez underwent shoulder surgery in December but said on the eve of the trip to the Gulf that he was "close to 100 percent".
His new teammate Jorge Lorenzo, who has switched from Ducati after a poor season which saw him miss four races with a wrist injury, was only 11th on Friday.
Veteran Valentino Rossi celebrated his 40th birthday last month but looked fresher than all his rivals in the first session on Friday, setting the fastest time on his Yamaha.
However, the Italian struggled in the second session, ending the day down in 16th place.
1. Marc Marquez (ESP/Honda) 1:53.380, 2. Maverick Vinales (ESP/Yamaha) at 0.474, 3. Jack Miller (AUS/Ducati-Pramac) 0.528, 4. Danilo Petrucci (ITA/Ducati) 0.673, 5. Fabio Quartararo (FRA/Yamaha-SRT) 0.774, 6. Andrea Dovizioso (ITA/Ducati) 0.876, 7. Franco Morbidelli (ITA/Yamaha-SRT) 0.895, 8. Alex Rins (ESP/Suzuki) 0.940, 9.Aleix Espargaro (Aprilia) 0.987, 10.Joan Mir (ESP/Suzuki) 1.022, 11. Jorge Lorenzo (ESP/Honda) 1.048
16. Valentino Rossi (ITA/Yamaha) 1.668