Qatar-backed PSG, who spent over 80 million euros on new players last summer, have looked far from convincing on the pitch but sit just three points behind Montpellier with both facing visits to struggling sides on Sunday.
"We're entering that phase where everything will be come down to mental toughness," Montpellier coach Rene Girard said prior to the southerners' trip to Lorient.
"And when you are in a battle with Paris...," he added, referring to PSG's numerous last-gap victories earlier this year. "But we are here and if they are better, they will show it on the field."
PSG, who have 63 points with seven games remaining, travel to bottom club AJ Auxerre, who lie seven points from safety and face an uphill battle to preserve their place in the elite.
"These kind of teams are always dangerous for us. They always give everything against PSG because it's PSG," goalkeeper Salvatore Sirigu told the club's website.
Montpellier once again showed they are well prepared for a dogfight with a 3-1 win at Marseille on Wednesday, with the prolific pairing of Younes Belhanda and Olivier Giroud proving more than a handful for most defences.
Morocco midfielder Belhanda was in inspired form and well worth his two goals, one of them a jaw-dropping volley, as Giroud chipped in with his 19th strike of the season.
"We can't hide anymore. We all firmly believe we will clinch the title," Giroud said on Wednesday.
Champions Lille, who are 10 points off the pace, will be looking to strengthen their hold on third place when they host AC Ajaccio, also on Sunday.
Lille occupy the Champions League play-off qualifying spot, three points ahead of seven-times champions Olympique Lyon, who face Marseille in the League Cup final on Saturday before making up the league fixture at Toulouse on Wednesday.
Holding midfielder Florent Balmont may be unavailable for Lille after he limped out of training on Tuesday with a muscle problem.