Hayden's motorcycle, who had begun training in his hometown at a private flat track in Kentucky, collided with another motorcycle.
The 30-year-old rider stated: "Of course injuries are never a good thing. But it's part of motorcycle racing. As in Valencia it was a terrible accident. I was starting to prepare again, as I do in the winter, at a private track near my house. I was behind another rider and he tried to get away from me. I wasn't going very fast but it hit my front wheel and I fell, I landed badly on my left shoulder and that was enough".
According to Ducati there are no plans for surgery at this time, but the situation with his champion's shoulder 2006 will be re-evaluated next week.
More generally the next few weeks are crucial for whether Hayden will take part in his first winter tests 2012 at 31 January in Sepang.
End, Hayden stated: "It's disappointing, but there is nothing I can do but hope to get better quickly. Be that as it may, this does not affect my expectations for the 2012, which is now very close".