The striker, who returned from injury last weekend with a goal, is in Uruguay for personal reasons, though the French coach says everybody else is fit and available
The forward returned to Uruguay earlier in the week for personal reasons and will not be back in time for Saturday's match and it is unclear whether he will feature in the Champions League last-16 second-leg tie with Bayer Leverkusen on Wednesday.
The 27-year-old, who has scored 14 goals in 22 league appearances for PSG this season, made a goalscoring return from injury at home to Olympique de Marseille last weekend but the Parisiens coach ruled out his involvement again.
"Cavani will not play tomorrow for the match against Bastia," Blanc told reporters. "I think apart from Cavani no other player will be unavailable.
"Christophe Jallet is back in the group, this will allow us to be able to breathe a little about Gregory van der Wiel."
Blanc is wary of the threat that Bastia will pose as PSG seek to extend their eight-point lead over Monaco, who host Sochaux later on Saturday.
"We know that we are in a very favourable position. But we must stay focused," the coach added.
"Bastia will want to exploit tomorrow, they are very motivated. We will try to be very effective in recovering the ball."
PSG attacker Jeremy Menez, who has been linked with a summer move to Atletico Madrid after falling out of favour at Parc des Princes, has been left out Blanc's squad for the visit to Bastia.