MOTEGI - Ducati's Andrea Dovizioso posted the quickest time over Friday's two rain-soaked free practices for the Japanese MotoGP Grand Prix as world champion Marc Marquez took a hair-raising afternoon spill.

The Italian clocked one minute, 54.877 seconds at Motegi with championship leader Marquez 0.2 seconds slower despite losing control of his Honda in the wet conditions.

It could have been worse for Marquez after his rear wheel gave way and he was flipped over his handlebars while screeching around turn four. Luckily for the Spaniard he skidded onto the gravel on the seat of his pants with the only real damage done to his pride.

"Everything felt perfect in the morning but I lost a bit of feeling after switching tyres for that last run in FP2," said Marquez, who insisted his crash would have little effect on his confidence in the title run-in. "Our speed was there and our lap times were good so I feel confident for the weekend," he added. "It's up to me to get the job done and not rely on good fortune."

Marquez went quickest in a morning session made treacherous by the rain, his time of 1:55.418 still the best until Dovizioso produced his fastest lap a quarter of an hour into the afternoon run.

Aleix Espargaro steered his Aprilia to the third fastest time after lunch, posting a late lap of 1:55.061, while Yamaha's seven-time premier class world champion Valentino Rossi was 12th quickest as he continues his return from a double leg fracture. Ducati's Jorge Lorenzo was fourth quickest combined, the triple world champion pipping Yamaha's Johann Zarco and Danilo Petrucci's Ducati.

Lorenzo also got away with one in the morning after colliding with Cal Crutchlow's Honda, sending both riders sprawling onto a run-off area before clashing angrily as marshalls tried to separate them.

Marquez clinched his third world title in Japan last year after Rossi and Lorenzo both crashed out. He opened up a 16-point lead over Dovizioso with four races left in this year's championship with his fifth win of the season at the Aragon race last month.