Alcaiz - Honda's Marc Marquez zoomed to the fastest lap in practice for the Aragon Grand Prix on Friday as the Spaniard seeks a fourth top-level victory on the track.
The reigning world champion, who has a massive 67-point lead in this year's title race, powered around the anti-clockwise Aragon Motorland track in 1min 47.382sec in the second free practice.
Marquez is known to love the track, on which turn No.10 was officially named as 'the Marc Marquez corner' last week.
"We made a big jump between free practice one and free practice two," Marquez told television channel Movistar. "Tomorrow we still have a lot to improve on."
Ducati have won the last two Grands Prix and the Italian team's pair of Jorge Lorenzo and Andrea Dovizioso were right behind their rival in second and third.
"The two Ducatis are going very fast," said Marquez. "We have to keep working on what happens when the tires start to wear, that will be the important part of the race."
Briton Cal Crutchlow, on a Honda, and Suzuki rider Andrea Iannone were fourth and fifth, around half a second slower.
Top 10 combined times:
1. Marc Marquez (ESP/Honda) 1min 47.382sec, 2. Jorge Lorenzo (ESP/Ducati) at 0.138, 3. Andrea Dovizioso (ITA/Ducati) 0.453, 4. Cal Crutchlow (GBR/LCR Honda) 0.480, 5. Andrea Iannone (ITA/Suzuki) 0.537, 6. Danilo Petrucci (ITA/Ducati Pramac) 0.752, 7. Dani Pedrosa (ESP/Honda) 1.007, 8. Alvaro Bautista (ESP/Ducati Angel Nieto) 1.070, 9. Valentino Rossi (ITA/Yamaha) 1.119, 10. Maverick Vinales (ESP/Yamaha) 1.170