The 47-year-old wants the Argentine to replicate his training displays in matches, while praising youngster Adrien Rabiot for his goalscoring performance
The Argentine star put in a sluggish performance, with Les Parisiens only breaking through in stoppage time at Parc des Princes after he had been replaced.
"He [Pastore] is a player who has many questions, perhaps asking too many of himself," Blanc told reporters after the match.
"He has trained to my complete satisfaction since I arrived. But there is still a mismatch between his training and his matches. He needs to find his best.
"We were asleep in the first half. But the players never gave up despite there only being a few minutes and they were rewarded."
Pastore's replacement, starlet Adrien Rabiot, set PSG on its way with a late goal and Blanc was delighted to see the club's youngsters stake their own claim.
"It makes me happy. We're built to offer them a little space. PSG is a club of high standards but also a club that trains young talent and character," he continued.
"I do not hesitate to trust Rabiot, [Hervin] Ongenda and [Kingsley] Coman."
PSG currently occupies second spot in the Ligue 1 table, one point behind leaders Marseille which has a game in hand.