Movistar Yamaha have confirmed Valentino Rossi suffered "displaced fractures of the tibia and fibula of his right leg" in a motocross accident. The MotoGP icon, a seven-time winner in the premier class, was hurt in a training activity on Thursday.
Reports in Italy suggested Rossi had suffered a suspected broken leg and this was duly confirmed in a statement from his team.
It read: "Following an enduro training accident on Thursday, August 31st, Movistar Yamaha MotoGP star Valentino Rossi was diagnosed with displaced fractures of the tibia and fibula of his right leg.
"The 38-year-old Italian rider will undergo surgery as soon as possible. A further medical bulletin will be issued later on Friday morning, Sept 1st."
Rossi broke the same leg in 2010, but returned after missing just four races.
His latest injury appears to end any hope the veteran had of claiming an eighth premier-class title in 2017. He trails championship leader Andrea Dovizioso by 26 points and appears all but certain to miss September's races at Misano and Aragon at the very least.