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The punishment drops the Ajo Derbi rider from fifth place to 10th.
Marquez had been leading the race until crashing on lap nine. He recovered and rejoined in 14th, before charging back through to fifth.
But he made a mistake on the penultimate lap and took a short-cut to regain the track, bringing him much closer to the three-rider group battling for fifth, which he then hacked through on the final lap.
The revised result means Marquez is now just four points ahead of today's winner Nico Terol and five clear of Pol Espargaro, who finished third at Indianapolis.
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