Les Phoceens have endured a dreadful run of form recently and have failed to win any of their last eight league games, slumping to ninth place in the process.
Didier Deschamps' men were eliminated from the Champions League in midweek, losing to Bayern Munich 4-0 on aggregate in the quarter-finals, and Mandanda has spoken of the dangers of facing a side second in Ligue 1.
"We need to be careful because Paris have individuals who can make a difference at any time. This is a match of Champions League standard," the keeper told France Football.
Mandanda then spoke of Marseille's recent woeful form and while admitting victory on Sunday will not make up for their recent slump, he hopes it will be enough to get the fans back on the team's side.
"A win against Paris does not erase all of these defeats, but it might help sort things out. I hope we can reconcile with the fans," he added.
"If we had a solution to our problems, they would have been solved. There is something wrong, we do not know where it came from but now we have to calculate. We have to fight for 90 minutes. Beyond playing well, the goal is to show solidarity and to hopefully win."
After facing PSG, Marseille then face league leaders Montpellier before contesting the Coupe de la Ligue final against Olympique Lyonnais on April 14, but the France international is simply concentrating on this weekend's match and hopes their opponents' recent dip in form may help.
"The game falls after Paris have had a series of defeats and that is a good coincidence. I hope it will revive us. We hope we're able to start afresh after this game," he concluded.