Gallopin suffered contusions to his left side and an undisplaced rib fracture on his right side.
Providing he recovers, the 30-year-old Frenchman will start his eighth Tour de France on Saturday, and will be hoping to add another stage victory to the one he won at the 2014 Tour, as well as supporting team leader Romain Bardet to help him improve on his third place of last year.
After four seasons with Belgian outfit Lotto Soudal, Gallopin made the decision to join AG2R La Mondiale this year, with his role there being to help Oliver Naesen in the Classics and Bardet at the Tour. Gallopin also wanted the opportunity to chase victories for himself, which AG2R manager Vincent Lavenu was happy to grant him.
This season, Gallopin won the Etoile de Bessèges stage race in February following victory in the final-stage time trial, and that ability against the clock means that he'll be a key player during the team time trial on stage 3 at this year's Tour. Before his crash on Sunday, Gallopin had finished second to AG2R teammate Pierre Latour in the time trial national championships.
"Non-displaced fracture of a rib following my fall at the French championship, inevitably very disappointed but confident and motivated for Le Tour!" Gallopin said on Twitter.
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The 2018 Tour de France starts on July 9 and concludes on July 29 in Paris. Cyclingnews will have complete live coverage from the race, as well as race analysis, blogs, video highlights and podcasts from the team on the ground.