PICTURES: Rossi's 'dirty' fall.

Valentino Rossi was left disappointed after crashing out of victory contention on lap 10 of Sunday's Indianapolis Grand Prix.

The Italian, who inherited the lead after Dani Pedrosa fell just in front of him on lap four, dropped out of a close second behind Fiat Yamaha team-mate Jorge Lorenzo when he lost the front into turn two (see below for more pictures).

The 30-year-old hit the asphalt hard with his right shoulder before sliding onto the grass. A stunned Rossi attempted to continue but his M1 was too badly damaged and he was eventually forced to accept his first DNF (and second non-score) of the season.

"Today is a disappointment of course," said Rossi. "We struggled here with the setting all weekend, but we made an improvement today and I got a good start and was able to stay in touch with Pedrosa.

"Once he fell, I knew it would be between Jorge and I but I honestly don't know how it would have finished, because Jorge was very fast today. Of course, it would have been better to have finished second than not to finish at all!"

Upon returning to the pits, Rossi immediately began checking the telemetry to try and find out what he had done wrong. The answer, it seems, is that the six time MotoGP champion had been a little off-line.

"Unfortunately I ran wide on to a dirty part of the track at turn one and lost the front," confirmed Rossi. "I tried to carry on but there was a problem with my throttle and it wasn't possible."

"It was a bit of a strange crash, and this is why as soon as Valentino got back he wanted to check the data," added team manager Davide Brivio. "It seems he just found himself on a dirty part of the track and so when he braked he lost the front and that was it."

Rossi's surprise error has halved his world championship lead to 25 points over Lorenzo heading into Misano, just a few miles from Rossi's home town.

"I want to congratulate Jorge for his victory and now we look forward to coming back to the front at Misano. We are still leading the championship and this is the most important thing," Rossi concluded.