Spain's Pedro Horrillo Munoz was taken to hospital after falling into a ravine during the eighth stage of the Giro d'Italia from Morbegno to Bergamo.
The Rabobank rider is in a serious, but not life-threatening, condition after the accident on the descent from San Pietro halfway through the 209km stage.
Horrillo has head and upper body injuries including several fractures.
Columbia rider Kanstantin Siutsou broke clear to win the stage, but Danilo Di Luca retains the overall lead.
The Italian finished third, behind Norway's Edvald Boasson Hagen who won stage seven, to keep the pink jersey.
But Siutsou's victory was overshadowed by Horrillo's horrific crash.
His bike was reportedly found around 60m away as paramedics recovered him from deep in a ravine.
On Friday, Lance Armstrong complained that the downhill finish to stage seven was too dangerous in heavy rain.
Sunday's ninth stage is a 165km circuit around Milan.