Paris Saint Germain ended a wretched week which saw them turfed out of the Champions League by Chelsea with a rare Ligue 1 loss, Laurent Blanc's side falling 1-0 at Lyon's Stade de Gerland on Sunday.
PSG, sorely missing injured star striker Zlatan Ibrahimovic, were undone by Jordan Ferri's first half goal.
The French captial side's mood was not improved by having the ball in the back of the net twice only for both to be ruled offside.
This loss, only their second of the season, left the expensively-assembled Qatari-backed team on 79 points, ten clear of Monaco at the top of Ligue 1 with five games of the season remaining.
While it is inconceivable they will fail to successfully defend their title this loss coming on the back of their Champions League failure may well raise questions over Blanc's future.
He is planning to decide on whether to extend his contract after next Saturday's French League Cup final at Stade de France....against Lyon.
"We thought we had got over the disappointment of our Champions League elimination, but in view of tonight's result this is not the case," said Blanc.
"We need to put this behind us."
As for Lyon this win, which cemented their grip on fifth place, came as a welcome fillip after being knocked out of the Europa League by Juventus in midweek.
PSG had the ball in the back of the net in the sixth minute but defender Lucas Digne was adjudged to be offside.
Shortly after a shot from Lyon striker Bafetembi Gomis hit the post.
Coach Remi Garde's men were unsettling PSG after the Parisiens' bright start and took the lead in the 31st minute.
Ferri nabbed the ball off PSG's Argentine attacker Ezequiel Lavezzi, the France Under-21 midfielder then looking up briefly before chipping right-footed over the head of advancing PSG keeper Salvatore Sirigu.
The ball thudded into the bottom right corner of the visitors' net to put a broad smile on the face of the home side's fans.
PSG went on the attack, trying to level before the break and could have pulled it off with a move involving Javier Pastore, Digne and Edinson Cavani but the Uruguayan's effort once he found space failed to trouble Lyon keeper Anthony Lopes.
On 63 minutes PSG had the ball in the back of the Lyon net for the second time but as in the first half Lavezzi's effort was disallowed with both him and Cavani ruled offside.
On 70 minutes Sirigu's quick reflexes denied Ferri doubling up with a shot from the right of the area.
Blanc shuffled his pack with ten minutes to go in a bid to unlock Lyon's defence which despite some close calls held firm.
Weekend results from Ligue 1:
Nantes 1 (Gakpe 4) Guingamp 0
Reims 2 (Charbonnier 24, Signorino 50) Saint-Etienne 2 (Brandao 51, Clerc 90+1)
Lyon 1 (Ferri 31) Paris Saint-Germain 0