The 48-year-old felt his side let themselves down with their second half display after missing out on the chance to clinch the Ligue 1 title
Victory would've seen the Ligue 1 leaders retain their title, but though Edinson Cavani got them off to the perfect start with the opener in the first half, the home side grew into the game in the second period.
And they were rewarded for their efforts when Thiago Silva put the ball into his own net just shy of the hour mark, with PSG unable to find the goal that would've clinched the title.
Blanc said: "We didn't get the three points so there has to be disappointment. We missed a lot of chances and Sochaux produced a very good performance.
"We scored a nice goal but it wasn't enough. They came back into the game in the second half and equalised, but we didn't do enough, so a drawn isn't illogical."
PSG midfielder Yohan Cabaye added his disappointment at failing to clinch the league crown and pointed to a lack of cutting edge in the final third.
"We lacked success in and around the penalty area," he admitted.
"There was more determination in the team that wanted to stay in the division than the one that wanted to lift the title.
"Unfortunately we are not champions tonight but we will stay focused and try and win against Rennes."