The defending champions could have secured a second successive French crown with victory at the Stade Auguste Bonal on Sunday, but were held to a 1-1 draw by a determined Sochaux outfit.
Edinson Cavani put the visitors ahead after 24 minutes, only for Sochaux to claim a valuable point in their quest for survival courtesy of PSG captain Thiago Silva putting through his own net early in the second half.
PSG can still wrap up the championship with two games to spare if they beat Rennes or Monaco fail to overcome Guingamp a week on Wednesday.
However, Blanc was quick to express his disappointment at his side's latest display.
"We came here looking for all three points, so we're disappointed with the result," Blanc said.
"We were a long way from our best and Sochaux played very well. We started well; we scored a very nice goal, but it wasn't enough.
"They (Sochaux) caused us real problems in the second half, they equalised and we didn't do enough to win it. The draw was the right result."
Midfielder Yohan Cabaye bemoaned PSG's lack of cutting edge in the final third.
"We lacked quality with the final ball, with the finish," Cabaye said. "We had a lot of chances. Sochaux played very well though.
"They showed a lot more determination and motivation to save their place in Ligue 1 than we did to win the league today.
"It's a poor performance and, unfortunately, we are not champions tonight. We have to stay focused, recover well and win against Rennes. That's the most important thing."
