The Ducati rider, who was already nursing a foot injury from the previous Aragon Grand Prix in Spain, was taken to hospital for a scan and said he had hurt his wrist.
"Really my wrist is very painful. It will need a lot of time to recover," he said in an interview posted on the MotoGP website (motogp.com) before qualifying on Saturday.
"For sure I decided not to take part in the Thailand Grand Prix which is a pity because I was doing great before the crash."
The three-times world champion, fourth in the MotoGP standings behind leader Marc Marquez, said he was in doubt to recover in time for the next race in Japan.
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(Reporting by Ian Ransom in Melbourne; Editing by Amlan Chakraborty)
