Championship leader Marc Marquez dominated a soaking first practice for the Japanese Grand Prix from Motegi, with Aprilia’s Aleix Espargaro his nearest challenger in second.

Avintia Ducati’s Hector Barbera was the early pacesetter in the sodden first session with a 2m00.685s, though this was soon eclipsed by Yamaha’s Maverick Vinales with a 1m59.344s.

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Typically finding the going tough in wet conditions on the YZRM1, Vinales – who is third in the standings and 28 points off of the lead – lowered his benchmark to a 1m58.303s with 30 minutes left on the clock.

Marquez demoted his fellow Spaniard almost immediately, however, with a 1m58.303s and improved to a 1m56.349s to go almost two seconds clear at just over half distance.

Nearest title rival Andrea Dovizioso – who comes into this round 16 points back – was able to briefly cut down the Honda rider’s advantage to 0.391 seconds as he jumped up to second, though was soon shuffled back to fifth while Marquez improved to a 1m55.418s.

As the field pushed on in the final few minutes, several riders were caught out by the conditions. Suzuki’s Andrea Iannone slid off his GSXRR at Turn 8, while Cal Crutchlow lost control of his LCR Honda under braking for Turn 9 and collided with Jorge Lorenzo – both walked away unscathed.

Aprilia’s Espargaro was a late improver on his RSGP in second spot, 0.875s off of Marquez’s best pace, while future teammate Scott Redding completed the top three on his Pramac Ducati.

Despite the incident with Crutchlow, Lorenzo ended the morning in fourth ahead of teammate Dovizioso, who will be somewhat concerned at the 1.2s gap separating him from Marquez.

Tech3 Yamaha’s Johann Zarco headed Crutchlow in sixth, while Alex Rins – who tested a new aerodynamic fairing this morning – finished up eighth quickest despite a late technical issue.

Vinales dropped to ninth at the chequered flag, while Bradley Smith – who was recently confirmed as remaining with KTM for 2018 despite speculation he would be replaced by test rider Mika Kallio – completed the top 10, with teammate Pol Espargaro 0.243s adrift in 11th.

Danilo Petrucci was second quickest at one stage, but his session was brought to a temporary halt as his Ducati GP17 ground to a stop exiting Turn 2. The Italian was able to return to circuit and was 12th ahead of Iannone and initial pacesetter Barbera.

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Kohta Nozane, who is replacing the unwell Jonas Folger at Tech3 this weekend, completed the top 15 in his first official MotoGP session, and was faster than factory rider Valentino Rossi (19th) and the Japanese rider’s fellow Yamaha tester Katsuyuki Nakasuga (23rd).

Hiroshi Aoyama completed the 24strong field in first practice, as he begind his duties as Jack Miller’s substitute for Marc VDS Honda while the Australian recovers from a broken right leg. Teammate Tito Rabat was an early faller in 21st, with Dani Pedrosa struggling ahead in 20th.