Former MotoGP world champion Nicky Hayden will have a delayed start to the 2012 season after a freak accident during training.
The American broke his left shoulder blade and suffered two fractured ribs in a fall while riding at a private track near his home in Owensboro, Kentucky.
It was the first time Hayden had been back on a bike since crashing out of the season-ending Valencia Grand Prix in early November.
The 30-year-old had scans during the week but will undergo further assessment in California to determine his progress.
"Obviously, injuries are never good," Hayden said in a Ducati statement.
"But it's part of motorcycle racing. Just like at Valencia, it was kind of a freak accident. I was starting to train again, like I normally do during the winter, at a private track near my house."
"I came up behind another rider, and he went to move out of the way. I wasn't going that fast, but he clipped my front wheel and I went down and landed pretty hard on my left shoulder, and that was it."
"It's disappointing, but there's nothing to do about it but heal quickly. Anyway, this doesn't change my expectations for 2012 which, fortunately, is just around the corner."
Hayden's injury puts in doubt his participation in the first winter test session of 2012, which begins in Malaysia on January 31.
The first race of the new MotoGP season will take place in Qatar on April 8.