The defending Ligue 1 champions missed the chance to go top as a Salvatore Sirigu error three minutes before half-time allowed Lille to cancel out Edinson Cavani's 29th-minute opener.
Without talismanic striker Zlatan Ibrahimovic - rested following his recent return from injury - Blanc's men were unable to find a second goal that would have ensured a 10th consecutive win and also taken them above Marseille.
While PSG were made to settle for a share of the spoils, Blanc explained there were positives to take from the game.
"Lille deserved to take a point," the Frenchman said.
"We knew that they would do everything to stop us from winning.
"We are disappointed, but at the same time, there were satisfying and encouraging signs for the future in this game."
Blanc also defended his decision to rest Ibrahimovic, who has struggled with heel problems in recent weeks.
According to the PSG boss, the Sweden international was always due to miss the game with a view to staying fit for the remainder of this year's fixtures.
"The calendar explains why Ibra was rested tonight. He needs to breathe and work to be ready for the run of matches before the winter break," he added.
"His injury is behind him but we are not able to easily get rid of pain that keeps you away for seven weeks.
"Playing again every three days would have been risky so, in agreement with the player, it was decided early on to rest at Lille."
