The Repsol Honda rider had been fastest in the drying morning; in the afternoon he slashed one-and-a-half seconds off that time, going even faster in the final shoot-out to underline a change in fortunes after a down-beat sixth place at Mugello.
At the track closest to his Cervera home, Marquez desperately needs to regain momentum for his title defence, after dropping to fourth overall as Marquez extended his lead. The omens were good, he felt. “This is the first Friday I have felt comfortable with the bike.”
With two minutes of the session left, Marquez deposed surprise leader Jorge Lorenzo on the factory Ducati; who had himself ousted Dani Pedrosa (Repsol Honda) one minute before, as the pace got hotter.
By the finish, Pedrosa had been pushed back to eighth. Jonas Folger (Monster Yamaha) was third, less than a tenth ahead of Andrea Dovizioso (Ducati), Danilo Petrucci (Pramac Ducati) and surprise sixth-placer Tito Rabat (EG-VDS Honda).
Johan Zarco (Monster Yamaha) was seventh; then Pedrosa and earlier leader Alvaro Bautista (Aspar Ducati).
Valentino Rossi (Movistar Yamaha) completed the top ten; while title-leading team-mate Maverick Vinales languished 16th-fastest, more than 1.7 seconds adrift, and in and out of the pits as he sought a solution to a persistent lack of grip.
But as usual on the first day, times depended on who had used soft tyres, while others relied on expectations of clear weather tomorrow.
By Michael Scott
Moto2 got the best of the morning weather. Unlike the other two classes, not everybody set his best time in the afternoon. One who did was points leader Franco Morbidelli.
The EG-VDS Kalex rider waited until the end of the session before surging into an impressive lead of better than three tenths … then fell unhurt on the following lap.
This knocked team-mate Alex Marquez to second; while Red Bull KTM’s Miguel Oliveira failed to improve from the morning, but his leading time from then was good enough to keep him third overall.
Taka Nakagami (Idemitsu Kalex) was fourth, then Simone Corsi (Speed Up) ahead of Mugello winner Mattia Pasini (Italtrans Kalex).
Before the final shoot-out, class rookie Jorge Navarro (Gresini Kalex) had led the time-sheets; Tom Luthi (CarXpert Kalex), Mugello runner up, was tenth; fast class rookie Pecco Bagnaia (SKY VR46 Kalex) ninth.
Times were close in Moto3, with the top 11 riders within one second, headed by EG rider Aron Canet heading a Honda trio. Romano Fenati (Rivacold Honda) was next, then runaway points leader Joan Mir (Leopard Honda).
Nicolo Bulega (SKY VR46 KTM) was fourth, ahead of Mugello first-time winner, his team-mate Andrea Migno.