The Paris Saint-Germain coach confirmed the Uruguayan striker will not be available in the next few weeks after suffering a thigh injury
Cavani limped off after 75 minutes of PSG's 2-0 win at the Parc des Princes on Friday, with scans concluding that the attacker had suffered a thigh injury.
The Uruguay striker will also miss Tuesday's Coupe de la Ligue trip to Nantes, and the PSG coach insists he will not rush the 26-year-old back from injury.
"Cavani has been ruled out against Nantes and will also be absent for Monaco," Blanc told reporters.
"His injury will be a matter of weeks. It is not uncommon for a player with his style of play [to pick up these problems].
"This is not a serious injury, but in order to prevent it getting worse, we will not take risks with Cavani."
Cavani, who joined PSG in a deal worth €64 million in July, has scored 20 goals in 30 appearances this season.
PSG sit five points above second-placed Monaco ahead of the trip to the Stade Louis II.