The world champion's Bora team announced that he had to abandon the race with around 70km to go after feeling unwell.
Sagan began the day as one of the favourites for victory having finished fourth last year and showed some scintillating form in the Belgian one-day races last week, Omloop Het Nieuwsblad, in which he finished second, and Kuurne-Brussels-Kuurne, which he won from a small breakaway group.
Bora said that Sagan has been feeling unwell before the race, but wanted to ride as much of it as possible despite being under the weather.
All eyes will now switch to the likes of Omloop winner Greg Van Avermaet (BMC Racing), who was another pre-race favourite alongside Sagan after showing some super form himself.
The pair will next face-off at the Tirreno-Adriatico stage race which begins on Tuesday. Van Avermaet goes in as defending champion, but both he and Sagan will be looking to gain some more form ahead of Milan-San Remo and the northern Classics in April.
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