Nicky Hayden suffered a nasty accident when he ran off track, couldn't stop and slammed into a tyre barrier - launching the American over the top and onto the road on the other side.
Hayden, who suffered a concussion and fractured hand at Indianapolis, was taken to the Medical Centre for checks where he has been declared 'ok'.
Stefan Bradl fell from third place early in the race.
Valetino Rossi ran straight-on after brushing the side of Jonathan Rea under braking on the opening lap.
Rea was again replacing injured reigning
MotoGP champion Casey Stoner.
CLICK HERE for pictures from the grand prix...
1.
Dani Pedrosa ESP Repsol Honda (RC213V)
42m 10.444s 2.
Jorge Lorenzo ESP Yamaha Factory Racing (YZR-M1)
42m 16.916s 3.
Andrea Dovizioso ITA Monster Yamaha Tech 3 (YZR-M1)
42m 21.491s 4.
Cal Crutchlow GBR Monster Yamaha Tech 3 (YZR-M1)
42m 21.628s 5.
Ben Spies USA Yamaha Factory Racing (YZR-M1)
42m 24.230s 6.
Alvaro Bautista ESP San Carlo Honda Gresini (RC213V)
42m 38.610s 7.
Jonathan Rea GBR Repsol Honda (RC213V)
42m 42.734s 8.
Valentino Rossi ITA Ducati Team (GP12)
42m 54.876s 9.
Karel Abraham CZE Cardion AB Motoracing (GP12)
43m 7.861s 10.
Aleix Espargaro ESP Power Electronics Aspar (ART CRT)
43m 8.969s 11.
Randy De Puniet FRA Power Electronics Aspar (ART CRT)
43m 10.307s 12.
Hector Barbera ESP Pramac Racing (GP12)
43m 25.005s 13.
Yonny Hernandez COL Avintia Blusens (FTR-Kawasaki CRT)
43m 26.603s 14.
James Ellison GBR Paul Bird Motorsport (ART CRT)
43m 27.024s 15.
Michele Pirro ITA San Carlo Honda Gresini (FTR-Honda CRT)
43m 36.259s 16.
Mattia Pasini ITA Speed Master (ART CRT)
43m 42.245s 17.
Danilo Petrucci ITA Came IodaRacing (Suter-BMW CRT)
43m 52.744s 18.
Colin Edwards USA NGM Forward Racing (Suter-BMW CRT)
+1 lap DNF: Stefan Bradl GER LCR Honda
MotoGP (RC213V)
David Salom ESP Avintia Blusens (FTR-Kawasaki CRT)
Nicky Hayden USA Ducati Team (GP12)