Cavani suffered the injury in a Ligue 1 game on Jan. 31 and was set to be out of action for three weeks, the club said at the time.
Blanc made it clear that although the striker's recovery was going well, he would not be ready for the last-16 first-leg match in Germany on Tuesday.
"It has never been considered that he could be available for Leverkusen," Blanc told a news conference. "But we will see him back very soon, all signs are very good."
Cavani has scored 20 goals in 30 matches in all competitions since joining the Ligue 1 leaders from Napoli last year for a French record fee of 64 million euros ($86.97 million).
PSG host Leverkusen in the return leg on March 12.