Andrea Iannone headed wildcard Michele Pirro by over half a second in the opening practice session for the MotoGP Italian Grand Prix.
Suzuki rider Iannone confirmed on Thursday at Mugello that he will be departing the Hamamatsu factory at the end of the year, with rumours linking him to Aprilia and a return to Pramac, for whom he rode in 2013 and '14.
Jorge Lorenzo, whose future is also uncertain, guided his Ducati to the top of the timesheets in the early stages of FP1 with a 1m49.132s, and reclaimed first place from former teammate Valentino Rossi on his follow-up tour with a 1m48.395s.
Championship leader Marc Marquez deposed Lorenzo just seconds later by 0.145 seconds, before Iannone leaped to the top of the times with a 1m48.086s.
Ducati wildcard Pirro – who will make his 50th race start this weekend – ended the succession of session-best laps with 34 minutes remaining when he took his GP18 to a 1m47.803s.
Pirro's time stood as the benchmark until the final 10 seconds of the session, when Iannone, who had switched to a fresh soft rear tyre for a late time attack, went 0.550s clear with a 1m47.253s.
Last year's Italian Grand Prix winner Andrea Dovizioso trailed Pirro by 0.158s with an early effort of 1m47.961s, while Yamaha's Maverick Vinales brushed off a tumble at San Donato in the opening minutes of FP1 to end up fourth fastest ahead of Pramac's Jack Miller.
Marquez found himself shuffled back to sixth at the chequered flag, while Franco Morbidelli headed mentor Rossi in seventh on his Marc VDS Honda.
Lorenzo was just 0.001s further back from Rossi in ninth, while Cal Crutchlow completed the top 10 on his LCR Honda, with Johann Zarco just outside of the Briton's time in 11th.
Tito Rabat took part in his first session since his vicious crash during a test at Barcelona, in which he suffered muscle damage to his left arm.
The Avintia rider was steady away at the start of the session, but improved to 21st with a 1m49.181s in the closing stages to go just four tenths shy of factory Honda man Dani Pedrosa in a lowly 17th.
Morbidelli's Marc VDS teammate Tom Luthi [22nd] was the only other faller in the session, the Swiss rider losing the front end of his RC213V at the Palagio corner with 13 minutes left on the clock.
