Slovenian star Tadej Pogacar was forced to retire from the Liege-Bastogne-Liege one-day classic on Sunday after a fall 85 kilometres into the race, organisers said.
The two-time Tour de France champion came into the Monument classic off the back of winning the Amstel Gold Race and the Fleche Wallonne.
Pogacar, the 2021 winner, crashed with Dane Mikkel Honoure who also had to pull out of the race.
His UAE Team Emirates teammates waited to help their leader catch up with the main group, but the 24-year-old could not continue.
Pogacar had been aiming to become only the third man to complete a hat-trick of Ardennes classic wins, after Davide Rebellin in 2004 and Philippe Gilbert in 2011.
Pogacar's misfortune left defending champion Remco Evenepoel as the race favourite.