Marc Marquez dislocated his left shoulder in a crash at the end of the 125cc practice session at Brno today.
The 17-year-old Spaniard, who is leading the championship with five victories so far this season, dropped his Red Bull Ajo Motorsport bike in the final minutes of the session while third fastest.
Marquez has a 26-point lead over Pol Espargaro in the standings, with Nicolas Terol 13 points further back in third.
Terol missed the last race at the Sachsenring due to the injuries he sustained in a crash at Barcelona, but set the fastest time in today's practice on his return.
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