Veteran Italian cyclist Michele Scarponi was killed on Saturday in a road accident while out training on his bike, his Astana team and Italian media said.
"This is a tragedy too big to be written," Astana wrote on Twitter, paying tribute to the 37-year-old, who won the Giro d'Italia in 2011.
"Ciao Michele," Astana added.
Scarponi was in the twilight of his career but proved his enduring quality on Monday when he took his first victory in four years, claiming victory in the opening stage of the Tour of the Alps.
He outsprinted Briton Geraint Thomas and Thibaut Pinot of France to claim the early lead of the race, a key warm-up event ahead of next month's Giro d'Italia, the first of the year's Grand Tours.
Scarponi died after being struck by a van near his home in Filottrano, central Italy, Astana and Italian media said.
He was gearing up for another tilt at the Giro, which starts on May 5.
Scarponi won the 2011 Giro after Alberto Contador was stripped of the title for doping.