Assen - Italian Francesco Bagnaia negotiated the slippery conditions to set the fastest time after Friday's first two practice sessions ahead of the Dutch MotoGP at Assen.
The Ducati rider had trailed in the first session under the rain but took advantage of the dry track in the second later in the afternoon for a quickest lap of 1min 46.877sec to edge out Spaniard Aleix Espargaro of Aprilia by 0.178sec.
The 25-year-old Italian is looking to make up for his fall last week when he was in pole position at the German MotoGP.
World champion Fabio Quartararo, who leads Espargaro in the overall standings this season, said he "preferred not to push to the maximum" in the rain and was third fastest for Yamaha at 0.305sec around the 4.542km Assen circuit.
"I saw that it was even a little bit dangerous, I didn't want to put myself in the red from the first session," said the French rider, adding he had "good feelings" and can "fight for a good result" on Sunday.
Ducati's Jack Miller initially dominated the morning session, but his time did not last long and the Australian finished fifth in a much faster second hour of testing on a warm tarmac.
Third in the championship before the 11th round out of 20, Frenchman Johann Zarco of Ducati-Pramac, slipped to ninth fastest.
"I'm still in the game no matter the conditions tomorrow (Saturday)," Zarco said.
"Otherwise in the dry there will be Fabio (Quartararo) and Pecco (Bagnaia), a bit angry about the fall on the Sachsenring," he warned.
Standings after first two practice sessions
1. Francesco Bagnaia (ITA/Ducati) 1min 46.877sec, 2. Aleix Espargaro (ESP/Aprilia) 0.178sec, 3. Fabio Quartararo (FRA/Yamaha) 0.305, 4. Alex Rins (ESP/Suzuki) 0.337, 5. Joan Mir (ESP/Suzuki) 0.559, 6. Jack Miller (AUS/Ducati) 0.625, 7. Maverick Vinales (ESP/Aprilia) 0.664, 8. Brad Binder (AFS/KTM) 0.853, 9. Johann Zarco (FRA/Ducati-Pramac) 1.012, 10. Marco Bezzecchi (ITA/Ducati-VR46) 1.038