Andrea Dovizioso has joined Nicky Hayden on the MotoGP injury list after also being hurt during a winter training accident.
Late on Thursday (January 5) the Italian, who is moving to Monster Yamaha Tech 3 for the 2012 season, wrote on his official Twtter page @AndreaDovizioso: "F***, I broke my right collarbone doing motocross."
Dovi also posted this picture.
Ducati rider Hayden broke his left shoulder blade and fractured two ribs at an indoor flat track facility near his hometown of Owensboro, Kentucky on December 27.
Both riders now face a fitness battle ahead of the crucial first 2012 MotoGP test session at Sepang in Malaysia, which starts on January 31st.
Dovizioso finished a career-best third in the 2011 MotoGP world championship, during his third and final season at Repsol Honda. He will ride alongside Englishman Cal Crutchlow at Tech 3 in 2012.
Crutchlow and 2011 Tech 3 team-mate Colin Edwards also broke collarbones last year - but during MotoGP events.
UPDATE: Dovizioso is expected to undergo surgery on Saturday.