MotoGP championship leader Valentino Rossi will start the final race of the season from the back of the grid after kicking Marc Marquez off his bike during the Malaysian Grand Prix.
Rossi finished third but was given three penalty points following a post-race investigation.
He later accused Marquez of "making me lose the championship".
Honda's Dani Pedrosa won the race, with Jorge Lorenzo second. The final race takes place in Spain on 8 November.
Rossi now leads Lorenzo by just seven points in the championship.
The Italian, whose team Yamaha have said they will appeal the sanction, said Spain's Marquez "rode only to cause me problems".
The incident happened on lap 13 of 20 after Rossi had gestured at Marquez following an overtaking move.
"Unfortunately, I lose a lot of time with Marc," the Italian explained. "And in turn 14, I tried to go a bit wide to take a better line and make him slow.
"He came to me and I think he crashed in that moment. His handlebar touched my foot and my foot slipped off, a bike can't crash only with a touch.
"He has won his fight, he made me lose the championship."
But Spaniard Lorenzo had called for Rossi to be punished, adding: "It's clear that he took Marquez off."
"Marquez did not play with both of us, he played only with me," Rossi said.
"He isn't playing fair. He would prefer Lorenzo to win. He is angry at me for a personal matter."
MotoGP race director Mike Webb said: "It's irresponsible riding causing a crash and for that we have imposed three penalties points on Rossi."
Rossi's lead means he will definitely win the title if he can finish in the top two in Malaysia, while Lorenzo must finish at least eighth to have any chance of depriving him.
Rossi is seeking his seventh MotoGP title, while 28-year-old Lorenzo is trying to win his third.
Malaysian GP result
1. Dani Pedrosa (Spa/Honda) 40 min 37.691 secs
2. Jorge Lorenzo (Spa/Yamaha) +3.612 secs
3. Valentino Rossi (Ita/Yamaha) +13.724 secs
4. Bradley Smith (GB/Yamaha) +23.995 secs
5. Cal Crutchlow (GB/Honda) +28.721 secs
Moto GP standings
1. Valentino Rossi (Ita/Yamaha) 312 pts
2. Jorge Lorenzo (Spa/Yamaha) 305 pts
3. Marc Marquez (Esp/Honda) 222 pts
4. Dani Pedrosa (Spa/Honda) 190 pts
5. Andrea Iannone (Ita/Ducati) 188 pts