Francesco Bagnaia's hopes of a fourth successive victory to keep the pressure on MotoGP series leader Fabio Quartararo suffered a blow on Friday as he was handed a three-place grid penalty for the San Marino Grand Prix.
The 25-year-old Ducati rider was judged to have impeded Alex Marquez during the morning's free practice.
A MotoGP statement said Bagnaia was found to have been "riding slow on the racing line, causing a dangerous situation for other riders.
"No appeal can be made which means the decision is final," the statement added.
Italian Bagnaia was second fastest after Friday's two practice sessions, 0.114sec behind compatriot Enea Bastianini as Ducati bikes claimed the first four places at Misano.
Championship leader Quartararo was fifth, 0.326sec off the pace after leading the times in the day's morning practice session.
Yamaha's Quartararo, also reigning world champion, leads third-placed Bagnaia by 44 points in the overall standings.
Bagnaia's teammate Jack Miller was third, 0.185sec behind Bastianini while Aprilia's Aleix Espargaro, who trails Quartararo by 32 points in the championship, was 0.412sec back in seventh.
Times from Friday's practice sessions at the San Marino MotoGP:
1. Enea Bastianini (ITA/Ducati-Gresini) 1:31.517, 2. Francesco Bagnaia (ITA/Ducati) at 0.114, 3. Jack Miller (AUS/Ducati) 0.185, 4. Johann Zarco (FRA/Ducati-Pramac) 0.320, 5. Fabio Quartararo (FRA/Yamaha) 0.326, 6. Maverick Vinales (ESP/Aprilia) 0.365, 7. Aleix Espargaro (ESP/Aprilia) 0.412, 8. Jorge Martin (ESP/Ducati-Pramac) 0.649, 9. Marco Bezzecchi (ITA/Ducati-VR46) 0.674, 10. Franco Morbidelli (ITA/Yamaha) 0.725