Nine-man Rennes defied the odds to hand Paris St Germain their second loss in as many home games, leaving Carlo Ancelotti's men wide open to conceding top spot in Ligue 1.
Romain Alessandrini proved in-form Rennes meant business with a fantastic volley in the 13th minute but the Breton outfit might have crumbled when goalkeeper Benoit Costil was sent off after Nene's leveller.
But Rennes would secure their third straight league win before the half-time whistle as Julien Feret whipped in a free-kick, with Frederic Antonetti frantically reorganising his men to weather the storm following Jean Makoun's second-half dismissal.
PSG, therefore, missed a valuable opportunity to pull clear of title rivals Marseille, who have two games in hand before tomorrow's trip to Bordeaux, with Les Girondins also ready to depose the capital club should they topple OM.
But PSG could slip from the summit as early as tonight, with St Etienne and Valenciennes both two points shy of the leaders and in action later this evening.
It was not long before Alessandrini rocked the Parc des Princes with a wicked volley from range following Feret's swift counter.
Mevlut Erdinc had carelessly spilled the killer ball from Feret, only for Zoumana Camara to clear just as far as Alessandrini's primed boot.
PSG hit back and Javier Pastore found Nene in a good position to beat Costil with ease in the 20th minute.
And Rennes' keeper was walking seven minutes later after colliding violently with the onrushing Jeremy Menez just outside the penalty area, leaving Cheikh N'Diaye to hastily pull on his gloves and take to the field for Erdinc.
There was a lack of clarity at the other end in the 34th minute, though, with Salvatore Sirigu left rooted to the spot as Feret rocketed his free-kick beyond a poorly organised wall and into the back of the net.
Both sides sniped at each other following the restart, PSG's Blaise Matuidi denied a shot following a mazy run, with Makoun seeing his bullet header rattle a post.
Rennes had been surprisingly comfortable with 10 men but the real challenge would be surviving the final 40 minutes after Makoun received a second yellow for a rash tackle on Nene.
There was no time to mull over the Rennes midfielder's departure as PSG came storming forward, Maxwell teeing up Guillaume Hoarau to smash the ball against the crossbar before Pastore forcefully clattered a post from the rebound.
It was a case of all hands to the pump as the hosts plundered forward at will, N'Diaye grateful as his defenders repelled strikes from Pastore and Hoarau, with Kevin Gameiro forcing the Rennes stopper to leap across his goal and keep out a ripping volley.
And the impressive N'Diaye stood tall for a frantic 10-minute finale, successfully parrying drives from Ezequiel Lavezzi, Alex and Pastore to edge Rennes up to fourth place, with a vulnerable PSG left in real danger of losing their grip on top spot.