Title contender Jorge Martin made the perfect start to FP1 as he led the way early on from Marco Bezzecchi.
The same couldn’t be said for Joan Mir, as the Spaniard’s wretched season continued as he suffered a big fall at turn eight.
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With cold conditions proving tricky, Alex Marquez was the next rider to go down as he lost the front-end of his Gresini Ducati at turn one.
Marquez’ team-mate Fabio Di Giannantonio then went quickest in what’s unlikely to be his final race weekend in MotoGP.
Linked with the second Mooney VR46 Ducati seat, Di Giannantonio is expected to win the battle against Fermin Aldeguer for that ride.
Despite his fall, Marquez remained in the top four as Ducati made an early statement of intent.
The top four riders were all aboard a Ducati and were split by less than a tenth, while Marc Marquez also made a great start to FP1 as he slotted into fifth - +0.080s down on Di Giannantonio.
The Repsol Honda rider was then bumped down to fifth as Enea Bastianini went P4 on the factory Lenovo machine.
Marquez then went fastest by nearly three tenths before Maverick Vinales put his Aprilia on top of the timingsheets.
After a very slow start to FP1, Bagnaia began picking up his pace as he went into the top ten for the first time with 15 minutes to go.
Briefly in last place before finding improvements, Bagnaia was struggling in sector one but was quick in the middle sectors.
Joining Mir in suffering a big fall at turn eight, Takaaki Nakagami went down late on as he also lost the front-end of his machine.
Martin once again showed very good pace late on as he moved up to second, however, it wasn’t enough to dislodge Di Giannantonio.
Johann Zarco then made it a Pramac Ducati double inside the top three by going nearly two tenths clear with his final effort.