Second-half goals to Evian's Clarck N'Sikulu and Modou Sougou denied PSG a 37th unbeaten match in all competitions.
Blanc was disappointed his side failed to take their chances but lauded Evian's 'heart' in managing to overcome PSG's early dominance.
"I did not see this defeat coming," Blanc said after Wednesday's game.
"This does not detract from the merit of Evian-TG who played with heart.
"They played very good in the second period and they would have been in trouble if we had taken our first-half opportunities.
"At 0-0, they could believe in their chances -congratulations to her."
PSG midfielder Blaise Matuidi was disheartened by the defeat but backed the club to rebound from the loss.
"In season, we knew we would have complicated games like this," Matuidi said.
"The key is to bounce back quickly and on Saturday against Sochaux."
