Alvaro Bautista went quickest at a drying Assen in Friday morning MotoGP practice, as Marc Marquez escaped a huge accident.
Marquez was the first rider to try slick tyres in the closing minutes.
The lap seemed to be going well until the approach to the very fast Ramshoek, just after the point where Jorge Lorenzo broke his collarbone on Thursday.
Marquez appeared to hit a damp patch and was thrown into a violent high-side, landing on his shoulders and then being collected by his sliding Honda before tumbling through the gravel.
Despite the ferocity of the crash, Marquez walked away unaided and was confirmed to be shaken but unhurt.
Meanwhile, off-track suggestions that Lorenzo would still attempt to race on Saturday swirled around the paddock, with Yamaha declining to rule the possibility out.
Lorenzo had successful surgery in Barcelona overnight, and is guaranteed a top-12 start if he is passed fit as his practice one time on a dry track held up as the fastest of the weekend so far, getting him into Q2.
On the circuit, Bautista eventually got down to the fastest wet time for Gresini Honda, then made successful use of slicks to set a 1m40.029s as the chequered flag came out.
That lap denied Aspar's Randy de Puniet the chance to top the session on his CRT Aprilia, the Frenchman ending up 0.194 seconds slower.
Two stand-ins were next up: Ben Spies' Pramac substitute Michele Pirro was third on the 'lab' Ducati in an unusual top 10, followed by Avintia's returnee Ivan Silva, deputising for Hiroshi Aoyama.
Marquez was classified fifth with his best wet-tyre time.
Works Ducati riders Nicky Hayden and Andrea Dovizioso plus Pramac man Andrea Iannone will all have to get through Q1 in qualifying as they were outside the top 10 in the weekend's sole dry practice session so far.
Pos Rider Team/Bike Time Gap Laps
1. Alvaro Bautista Gresini Honda 1m40.029s 17
2. Randy de Puniet Aspar Aprilia 1m40.223s + 0.194s 15
3. Michele Pirro Pramac Ducati 1m45.601s + 5.572s 10
4. Ivan Silva Avintia FTR-Kawasaki 1m46.724s + 6.695s 17
5. Marc Marquez Honda 1m46.761s + 6.732s 13
6. Cal Crutchlow Tech 3 Yamaha 1m46.981s + 6.952s 8
7. Andrea Dovizioso Ducati 1m47.014s + 6.985s 13
8. Nicky Hayden Ducati 1m47.027s + 6.998s 10
9. Dani Pedrosa Honda 1m47.055s + 7.026s 12
10. Karel Abraham Cardion Aprilia 1m47.782s + 7.753s 12
11. Yonny Hernandez PBM Aprilia 1m48.067s + 8.038s 10
12. Valentino Rossi Yamaha 1m48.167s + 8.138s 11
13. Andrea Iannone Pramac Ducati 1m48.396s + 8.367s 12
14. Claudio Corti Forward FTR-Kawasaki 1m48.495s + 8.466s 11
15. Bradley Smith Tech 3 Yamaha 1m48.822s + 8.793s 9
16. Aleix Espargaro Aspar Aprilia 1m48.976s + 8.947s 10
17. Danilo Petrucci Ioda-Suter-BMW 1m49.066s + 9.037s 11
18. Michael Laverty PBM-Aprilia 1m49.259s + 9.230s 6
19. Hector Barbera Avintia FTR-Kawasaki 1m49.312s + 9.283s 12
20. Bryan Staring Gresini FTR-Honda 1m49.637s + 9.608s 16
21. Lukas Pesek Ioda-Suter-BMW 1m50.501s + 10.472s 13
22. Stefan Bradl LCR Honda 1m50.830s + 10.801s 5
23. Colin Edwards Forward FTR-Kawasaki 1m52.118s + 12.089s 9