Lyon has fallen three points off of PSG's pace in the race for the Ligue 1 title after losing to Ajaccio, 3-1, at the Stade Francois Coty on Sunday.
After a scoreless opening period, Andrew Lacazette had given visiting Lyon the lead in the 53rd minute, but it was quickly canceled out by Chahir Belghazouani four minutes later.
Adrian Mutu scored in the 65th minute to hand Ajaccio the lead, and Lyon wasted a tremendous opportunity to get on level terms with three minutes to go when Bafetimbi Gomis failed to convert a penalty kick.
Things went from bad to worse for the visitors as Dejan Lovren was sent off in the final minute before Mutu converted from the spot to seal the win for Ajaccio, which improves to 25 points to pull five points clear of the relegation zone.
Lyon remains on 45 points for the season, falling three points behind first- place PSG after its resounding 4-0 defeat of Toulouse on Friday.
Marseille failed to capitalize on Lyon's slip-up as it fell to Nancy in a 1-0 loss at the Stade Velodrome on Sunday.
Joey Barton was sent off in the 59th minute, but things got worse for Marseille as Andre Ayew's own goal saw the club remain on 42 points, three points back of second-place Lyon. Nancy improves to 18 points to climb out of the Ligue 1 cellar.
Rounding out the Ligue 1 action on Sunday, Montpellier overturned a one-goal deficit to earn a 3-1 victory over Reims as Souleymane Camara, Marco Estrada and Younes Belhanda each recorded a second-half goal en route to the win.