Paris: Serhou Guirassy's second-half header helped Rennes secure a 1-1 draw against Paris Saint-Germain at Roazhon Park on Sunday, damaging the Parisians' hopes of a fourth consecutive Ligue 1 title.
Mauricio Pochettino's side needed a win to keep pace with league leaders Lille, who claimed a comfortable 3-0 victory at Lens on Friday.
Neymar, who had signed a contract extension until 2025 on Saturday, put PSG ahead in the first-half injury-time when he converted a penalty awarded by VAR for a foul on Layvin Kurzawa.
However, this was not enough to secure three points for the visitors, as Guirassy headed home an equalizer from Benjamin Bourigeaud's corner.
PSG are now three points behind leaders Lille with only two matches remaining. The capital outfit are also under threat from third-placed Monaco, who now trail PSG by only two points after a 1-0 win at Stade Reims.
Should Monaco surpass PSG, the capital side would have to contest the final qualifying round of next season's UEFA Champions League in order to make it into that tournament's group stages.
"Of course it's a blow to morale. We will believe until the end, but we have to do a lot better at PSG. We know it's difficult and Lille wins every game, but we have to believe we can win the title and win our last matches," PSG captain Marquinhos told French television after the draw.
Lille have won five of their last six league matches, including a 1-0 victory over PSG in early April and a crucial 3-2 victory against fellow title contenders Lyon two weeks ago.
The northern outfit, which was sold to a Luxembourg-based investment fund in mid-season, is on the brink of clinching their first Ligue 1 title since the 2010-11 season.
"It's clearly not our best season. We weren't very strong and we have to do a lot better. We need to talk to each other for next season." Marquinhos added.
The disappointing draw made the week even worsen for Pochettino, as his team had been knocked out of the Champions League semifinals by Premier League side Manchester City on Tuesday.
"We are all disappointed because today was a must-win game and we didn't offer the performance that we expected," Pochettino admitted. "We need to move forward, we cannot wait and it's our responsibility and our obligation to always be ready for the next match."
PSG will host Stade Reims in their next Ligue 1 match on May 16, after their French Cup semifinal clash against Montpellier on May 12.
Earlier, Marseille faded at Geoffroy Stadium in a 1-0 defeat to Saint-Etienne, which casts doubt on its bid for a UEFA Europa League spot.
Marseille sit fifth, level on points with Lens but ahead on goal difference. Only a top-five finish will secure a ticket for next season's continental competitions