The World Cup winner was enthused by the way in which his side responded to going a goal and a man down at the Stade Velodrome
The Ligue 1 champions appeared to be heading for defeat 11 minutes before half-time when Andre Ayew gave Marseille the lead from the penalty spot following Thiago Motta's foul on Mathieu Valbuena, with the Italy international's indiscretion also earning him a red card.
However, PSG overturned the deficit despite Marseille's numerical advantage, with Maxwell equalising with a header on the stroke of half-time, before Zlatan Ibrahimovic netted the winner from the spot after Ayew had brought down Marquinhos.
"The will was a very important element of this game because without it we could do nothing," Blanc told reporters after the game.
"There was also an impressive solidarity and quality in the game. For this kind of game you need good players and a good state of mind.
"We always believed despite the penalty and the red card. At half-time we were glad to have equalised but we wanted to win."
PSG, who move level on points with leaders Monaco, will look to continue their unbeaten start to the season after the international break when they welcome Bastia to the Parc des Princes.