Steegmans' team estimate he will be out for just three weeks
Belgian cyclist Gert Steegmans broke a collarbone after being caught in a whirlwind in the Paris-Nice prologue.
The RadioShack member was lifted off the ground as he sped 75km/h (47mph) downhill during Sunday's time-trial.
An eye-witness from the RadioShack team, Dirk Demol, said: "Tree branches flew in the air and a second later Gert was lifted in the air too.
"He was blown away from the road and tumbled over and over many times. I've never seen such a thing in my life."
RadioShack, the current team of seven-time Tour de France winner Lance Armstrong, confirmed Steegmans also injured his shoulder and suffered "road rash" (grazing) all over his body.
However, the team estimated the 29-year-old sprint specialist, who was expected to be RadioShack's leader in the upcoming classics races, will return to training in just three weeks, using plates and screws to secure his fracture, with the operation scheduled for Monday.
"It took 12 minutes for the ambulance to arrive while we waited and could do nothing," Demol added.
"Gert was screaming all the time. He seemed to have broken more than one thing."
Holland's 2008 world cyclo-cross champion Lars Boom won the prologue, staged in the town of Monfort-l'Amaury just outside the French capital.
German veteran Jens Voigt came second, with American Levi Leipheimer taking third.
Britain's David Millar finished seventh, covering the 8km route in 11 minutes and seven seconds, while Welshman Geraint Thomas was the highest of Team Sky's finishers, coming in 15th.
The eight-stage, 800-mile race ends next Sunday in Nice.