The Italian Ducati rider - currently fifth in the championship standings - crossed the line in one minute and 49.195 seconds in a rain-affected FP2 to come out on top.
Pramac's Yonny Hernandez (+1.115secs) delivered the goods in the earlier FP1 to register the second fastest time of Friday, while Repsol Honda's Dani Pedrosa (1.161secs) was third.
Hernandez was the only rider to post a worse time in the second session than he had in the first - completing his quickest lap four tenths slower in FP2.
Pedrosa's team-mate Marc Marquez has won 11 of the 12 rounds so far this season, but was 1.324 seconds off the pace in fourth on Friday.
Danilo Petrucci (+1.446secs) of IodaRacing Project rounded off the top five, while Yamaha's Valentino Rossi was 10th fastest following a fall in the first session.
In other MotoGP news, it was confirmed on Friday that Aprilia would return to the series in 2015, with Gresini Racing set to run prototypes in a contract that extends to 2018.