Blanc's men saw their lead cut to two points after a shock 2-0 defeat at Evian earlier this month and the coach was also annoyed by his side's performance in their 2-1 UEFA Champions League loss at Benfica on Tuesday.
Despite PSG having long since sealed their place in the knockout stages, Blanc warned his players the performance was unacceptable and says nothing less than three points will do at Rennes.
Blanc said: "We must take maximum points from our next two games. We were frustrated and disappointed by the defeats at Evian and Benfica and I want a reaction.
"You can lose matches but you have to give the best of yourselves in every game and we did not do that. The president has a requirement to become champions and to go as far as we can in the Champions League."
Blanc does not expect to have any new injury worries for the trip to the Stade de la Route de Lorient with the exception of right-back Christophe Jallet, who faces a late test on a calf complaint.
Rennes go into the game on the back of a disappointing 2-0 defeat at Lorient last Saturday but coach Philippe Montanier insists he cannot fault his players and is undaunted by the threat posed by the leaders.
Montanier said: "Paris have taken another dimension this year, but we must give everything and hope to get a result.
"I have nothing bad to say about my players from the last two games. We must continue along the path we are on, and I know all my players are very eager to play in this game."