125cc World Championship leader Marc Marquez has been diagnosed with a dislocated left shoulder after a highside fall at the end of Friday practice for the Czech Republic Grand Prix at Brno.
The Red Bull Ajo Derbi rider, who dislocated his right shoulder earlier in the year at Jerez, has won the last five races and leads the championship by 26 points from Pol Espargaro.
Marquez was third fastest in the session behind the Aspar Aprilias of Nico Terol and Bradley Smith, with Espargaro in fourth.
Despite the injury, Marquez will try to ride on Saturday.
"Right now, it hurts a bit but, given the circumstances, I feel quite good and that makes me feel positive," he said. "It was quite a fast fall and I hit the floor sharply which put my shoulder out.
"Tomorrow, if the doctor lets me, we'll try to do a few laps and then assess the situation. It's similar to the injury from Jerez although here they reduced the dislocation more quickly.
"The shoulder came out forwards instead of upwards and it doesn't hurt so much. As soon as they got me to the circuit hospital, Doctor Costa put it back in place and I would like to thank him for his work because it wasn't necessary to sedate me, unlike in Jerez.
"It was faster, less painful and they treated me really well. Tonight, I'll get a good night's sleep and tomorrow, when I wake up, we'll see how I am and decide if I try to go for the morning or leave it until the official qualifying session."