Honda rider Marc Marquez dominated the third MotoGP practice session at Argentina's Termas de Rio Hondo circuit, as both works Ducati riders missed out on automatic Q2 spots.
A wet-weather session left championship leader Andrea Dovizioso and team-mate Jorge Lorenzo - as well as Pramac rider Danilo Petrucci, also riding a 2018-specification Ducati - outside of the combined practice top 10, after the Italian marque's bikes struggled on Friday.
Rain overnight followed by overcast conditions in the morning meant the track surface did not dry in time for third practice, and riders were forced to wet-tyre test.
Marquez seized the top spot in the opening minutes, but was soon surpassed by Dovizioso, before Tech3 duo Hafizh Syahrin and Johann Zarco also took turns at the front.
But the reigning champion reclaimed the lead with the session's first sub-1m51s lap, before subsequent improvements shuffled him down the order.
Yet Marquez saved his best for last, logging a 1m48.896s in the final seconds - which left him comfortably in first place, despite being over nine seconds down on his Friday benchmark.
Zarco improved at the chequered flag to cut Marquez's advantage to 0.607s, while Nieto Ducati duo Alvaro Bautista and Karel Abraham were the only other two riders to get within a second of the Honda man.
Petrucci made it three Ducatis in the top five in FP3, followed by LCR's Cal Crutchlow and KTM rider Pol Espargaro, with Syahrin, Dovizioso and Dani Pedrosa making up the top 10.
While both works Ducati riders will have to fight their way through Q1, the rest of MotoGP's leading factories are assured of having their bikes in the pole shoot-out.
Marquez and Pedrosa will be joined in Q2 by Crutchlow on his privateer Honda, with Suzuki riders Andrea Iannone and Alex Rins and Valentino Rossi and Maverick Vinales of Yamaha also booking their spots.
Zarco and Pramac Ducati's Jack Miller are in as well, as the two riders to advance on the strength of their FP1 times.
Miller is joined by fellow GP17 rider Tito Rabat - the only other Ducati to make sure of a Q2 spot.
|2||Johann Zarco||Tech3 Yamaha||Yamaha||0.607s||21|
|3||Alvaro Bautista||Aspar Ducati||Ducati||0.932s||20|
|4||Karel Abraham||Aspar Ducati||Ducati||0.996s||15|
|5||Danilo Petrucci||Pramac Ducati||Ducati||1.052s||15|
|6||Cal Crutchlow||LCR Honda||Honda||1.253s||13|
|8||Hafizh Syahrin||Tech3 Yamaha||Yamaha||1.365s||18|
|17||Tito Rabat||Avintia Ducati||Ducati||2.155s||20|
|18||Franco Morbidelli||MVDS Honda||Honda||2.274s||19|
|21||Takaaki Nakagami||LCR Honda||Honda||2.740s||20|
|22||Thomas Luthi||MVDS Honda||Honda||3.456s||17|
|23||Xavier Simeon||Avintia Ducati||Ducati||3.566s||18|
|24||Jack Miller||Pramac Ducati||Ducati||3.752s||6|