The Frenchman, who was set to kick off his year with a defence of his Etoile de Bessèges title on February 3, has suffered from knee pain for 10 days, according to a statement released by his team.
A medical check-up didn't turn up any lesions or damage, but his training schedule has been altered as a result.
No set date has yet been announced for Cosnefroy's rescheduled return to racing, though he should be back by March.
"The pain is disabling during long physical efforts," said Cosnefroy in a statement. "It should be better to wait. I'll continue to train to be competitive in March races."
The 25-year-old, who won the under-23 road race at the Bergen World Championships in 2017, has improved year on year after turning pro with the French squad in 2018. He has nine pro wins to his name – all in France – including the Tour du Limousin and Paris-Camembert in 2019, and the GP Marseillaise last season.
2020 also saw Cosnefroy announce himself as a major player in the hilly Classics, finishing second at La Flèche Wallonne and Paris-Tours, and third at Brabantse Pijl after a late battle with world champion Julian Alaphilippe (Deceuninck-QuickStep) and Dutch superstar Mathieu van der Poel (Alpecin-Fenix).
He'll target Ardennes week this spring as his team retools to focus on the Classics after the departures of GC men Romain Bardet and Pierre Latour.
Perennial cobbled contender Greg Van Avermaet has joined on a three-year deal, while 2018 Liège-Bastogne-Liège winner Bob Jungels has also signed up, joining Cosnefroy and Oliver Naesen to form a strong Classics core.
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