Movistar rider Xavier Tondo has died in a freak accident at a ski resort in southern Spain.
The 32-year-old Spaniard was crushed between his car and a garage door as he prepared to set off for training, local police said.
Tondo finished sixth in the Vuelta a Espana in 2010 and won the Vuelta a Castilla y Leon in April.
"He was an incredible person who loved this sport more than anyone," said Tour de France champion Alberto Contador.
Tondo was one of a number of cyclists preparing for the Tour de France at altitude in the Sierra Nevada resort, near Granada.
The manager of his Movistar team, Eusebio Unzue, said another Spanish professional cyclist, Benat Intxausti, of the Euskaltel team, was in the vehicle at the time.
"How life is unfair and sometimes difficult to understand," fellow Spaniard Contador said on Twitter.
"I can't describe how I feel after the death of Xavi Tondo. My most sincere condolences to his family. You will be sorely missed. Rest in peace."
Earlier this year, Tondo lifted the lid on a doping ring when he informed authorities after receiving emails in which he was offered banned substances.
His death is the latest tragedy to hit the sport after Belgian cyclist Wouter Weylandt died in a crash in the Giro d'Italia earlier this month.