MotoGP rookie Cal Crutchlow fractured his left collarbone - and suffered concussion - during a hard fall in the opening minutes of qualifying for his home British MotoGP at Silverstone on Saturday.
The injuries come just eight days after Monster Yamaha Tech 3 team-mate Colin Edwards broke a collarbone at Catalunya and means the MotoGP grid will be reduced to just 15 riders for Sunday's race.
Edwards, who had surgery to help his injury heal, has returned to action this weekend, but Repsol Honda's Dani Pedrosa is still sidelined with his broken collarbone.
Crutchlow, who had been top-six in all three free practice sessions at Silverstone, slammed his left shoulder into the asphalt after being kicked from his M1 on entry to Turn 2 on his third lap of qualifying.
Crutchlow wears Spidi leathers, which are not thought to have an air bag system fitted (as available for Dainese and Alpinestars MotoGP riders).
The Englishman won both WSBK races from pole at Silverstone last season. He had been hoping to fight for a front-row start this afternoon, after spending his first five races on unfamiliar tracks.
"Cal's injury is a very big disappointment and I feel really sorry for him because he was desperate to do well in his home race here at Silverstone,2 said team manager Herve Poncharal.
"He's been fast all weekend, so we had high hopes that he could get a good place on the grid and be challenging for the top six in the race. But track conditions were quite cold and it was obvious from looking at the TV pictures that the tyre wasn't up to temperature.
"He is in pain right now but I think he is more upset than anything else because he wanted to put on a good show for the British fans.
"A lot of people have come to support him and he didn't want to let anybody down.