Loris Capirossi has been ruled out of the Japanese MotoGP next weekend with a dislocated shoulder.
The 38-year-old, who has already announced that he will retire at the end of the season, suffered the injury in a crash at Aragon last Sunday.
The former 125 and 250cc world champion hopes to be fit enough to return for the race in Australia on 16 October.
He said: "My shoulder hurts, and it will take at least two weeks of full rest plus a week of rehabilitation."
Capirossi has endured a dismal final season and has already missed three races after breaking two ribs in Assen.
His best finish for his Pramac Ducati team this season was ninth in Catalunya.
"I wanted to race in Japan, one of my favourite tracks where I have achieved many good results and much satisfaction, but the doctors were more than clear," he added.
"I regret this very much, but I think this is the best choice for ending my season, and my career, in the best way possible for the last three races in Australia, Malaysia and Valencia."
Doctor Costa Claudio said: "I saw Loris's fall, which was spectacular and of course very dangerous.
"He again suffered a dislocation of the right clavicle, which he had already dislocated at the Netherlands Grand Prix.
"If he were to have another similar accident, with the ligaments that have just healed and are therefore no longer totally healthy, it could be dangerous and not worth the risk."