Valentino Rossi fractured his right tibia during a huge highside during the second practice session at Mugello today. A Clinica Mobile doctor attending the scene described the fracture as "serious" saying, "it's an exposed fracture with the bone protruding from the skin...which fortunately has not affected any blood vessels or nerves." Because of the injury, Rossi will not be able to race tomorrow, the first time he's missed GP since his debut in the 125cc class in 1996.
Update: Turns out Rossi fractured both his tibia and fibia. Surgery was a success and he'll make a full recovery, but it'll be four to five months before he'll be able to ride a bike again.
The incident occurred at the top of the turn 13 chicane. Judging by
these pictures, Rossi landed on his right leg, which can clearly be seen
bending at the top of his boot. It's currently unknown how many races
Rossi will be sidelined due to the injury, but it's sure to end any
hopes of a seventh MotoGP world championship this season.
MotoGP.com via Ash On Bikes