Andrea Dovizioso pipped Marc Marquez in practice on a wet opening day at the Japan Grand Prix on Friday.
The title rivals took honours in a session each at Motegi – with Marquez topping the opener before Dovizioso responded later.
The Italian Ducati rider set a time of one minute, 54.877 seconds in second practice to top the overall timesheets for the day.
Winner of the past two races and holding a 16-point lead atop the riders' standings, Marquez – who claimed victory in Japan last year – was just 0.043 seconds slower.
But the Spanish Repsol Honda rider pushed too hard late in the second session.
After running off just minutes earlier, Marquez fell at turn four after a dramatic wobble.
Aleix Espargaro (Aprilia Racing Team Gresini), Jorge Lorenzo (Ducati) and Johann Zarco (Monster Yamaha Tech 3) made up the top five fastest for the day.
In the opening session, Lorenzo was sideswiped by Cal Crutchlow at turn nine, but he finished the session.
Like almost all riders, Valentino Rossi improved in second practice, but he could only set the 12th fastest time of the day.