Andrea Iannone topped the timesheets in both Friday practice sessions for the Dutch TT, a race he will start from the back of the grid.
Iannone, penalised for colliding with Jorge Lorenzo in Barcelona last time out, pipped Ducati team-mate Andrea Dovizioso to first place in FP1.
And Iannone again proved fastest in FP2, edging out fellow Italian Valentino Rossi (Movistar Yamaha) by just 0.004 seconds with a time of one minute and 33.591secs.
Championship leader Marc Marquez (Repsol Honda) took third in session two, which saw riders pushing hard with rain forecast for Saturday morning in Assen.
The top five in FP2 was rounded off by Maverick Vinales (Suzuki Ecstar) and Lorenzo (Movistar Yamaha),