Olympic champion Annemiek van Vleuten suffered a broken pubic bone after crashing in an incident-packed inaugural Paris-Roubaix Femmes on Saturday.
The Dutch rider was one of many to hit the deck as rain produced treacherous conditions on the fabled cobbles.
"Not a 2021 happy end for me. Stupid crash. Just wanted to go to the finish safe," the 38-year-old posted on Twitter.
"Result is broken pubic bone in 2 places and a long recovery staying in bed coming up. Bye bye holiday. Bye bye recharging. I have done this more often but energy is running out."
Three-time world champion Van Vleuten has enjoyed an impressive season with wins at the Tour of Flanders and Challenge by La Vuelta as well as finishing second in the Olympic road race and winning gold in the time trial.
Britain's Lizzie Deignan won the Paris-Roubaix race in its first edition for women riders with Van Vleuten's compatriot Marianne Vos coming second.
(Reporting by Martyn Herman; Editing by Toby Davis)