MotoGP rookie Marc Marquez set the pace during drying conditions in opening free practice for the Italian Grand Prix at Mugello.

The Texas winner was among a handful of prototype riders to fit slick tyres in the closing minutes and finished with an advantage of 0.398s, despite running on and then falling on the wet grass at the very end of the session.

Ducati test rider and wild-card Michele Pirro put his numerous Mugello testing laps to good use by being second quickest on the Desmosedici 'lab' bike.

LCR Honda's Stefan Bradl, Cardion AB's Karel Abraham and PBM's Yonny Hernandez completed the top five.

Hernandez had been one of the first to fit slicks, shortly after the halfway stage, when he replaced Marquez's Repsol Honda team-mate and title leader Dani Pedrosa at the top of the timesheets.

Pedrosa, like factory Yamaha riders Jorge Lorenzo and Valentino Rossi, opted not to take risks on slicks and the trio were left down the order as a result.

The tricky conditions saw numerous incidents, the most notable of which was a heavy lowside fall for Andrea Dovizioso. Dovi, starting his first home weekend as a Ducati rider, walked away unharmed.

Pramac Ducati's Ben Spies, returning to action after missing the last two races to rest his healing shoulder, was tenth quickest.

Free Practice 1:
1. Marc Marquez
2. Michele Pirro
3. Stefan Bradl
4. Karel Abraham
5. Yonny Hernandez
6. Bradley Smith
7. Nicky Hayden
8. Dani Pedrosa
9. Cal Crutchlow
10. Ben Spies
11. Alvaro Bautista
12. Aleix Espargaro
13. Andrea Iannone
14. Jorge Lorenzo
15. Andrea Dovizioso
16. Hiroshi Aoyama
17. Colin Edwards
18. Randy De Puniet
19. Valentino Rossi
20. Hector Barbera
21. Lukas Pesek
22. Bryan Staring
23. Danilo Petrucci
24. Michael Laverty
25. Claudio Corti