The Parisians coach says the club's unconvincing performance against Ajaccio was down to its midweek exertions in the Coupe de France.
Blanc's side came from behind to take the points in Corsica, Ezequiel Lavezzi and Blaise Matuidi turning things around for the visitors after Brazilian striker Eduardo had put Ajaccio ahead.
Still, the former France coach was disappointed with PSG's start to the match, although he conceded that their exertions in Wednesday's 5-2 Coupe de France win at Brest may have had an impact on the game.
"It was a very bad start," Blanc said. "We were aware that it was a tough match, we had to try and make it as easy as we did in the Coupe de France.
"We were a little tired from Wednesday, so that may be why we were a little slow to start. We had to be very efficient in the in the first 20 minutes, we were not, and then we conceded a goal where we showed passivity.
"It galvanized them, but we had the good idea to equalise, allowing us to level the score and get back into the match."
Blanc was irritated with PSG's lack of composure at both ends of the pitch and he urged his side to refocus its concentration on the league following the mid-season break.
"At a few points in the second half we could have pulled away," he added. "We must score the third goal (after going 2-1 up). In some situations, we did not do the right thing at the right time.
"Even though it was a laborious match, we had 71 percent of possession. What bothered me is that, with every Ajaccio attack, we looked agitated.
"These matches are difficult for everyone. There was a short break, our bodies and minds must get back into the competition."