A weakened PSG (Paris Saint-Germain) lost a second straight game in all competitions to Monaco 3-1 in the French league on Saturday, three days before facing Bayern Munich.
Monaco climbed to third place, seven points behind a rattled PSG, whose lead was cut to five points after second-placed Marseille beat Clermont 2-0.
Undefeated in all competitions from August to December, PSG has become fragile. It lost to Lens and Rennes in the league last month and was knocked out by Marseille in the last 16 of the French Cup on Wednesday.
“We have conceded a lot of goals since the restart of the season,” PSG coach Christophe Galtier said. “We must rediscover our balance, defensively.”
Lionel Messi and Kylian Mbappe were out injured but Neymar played.
Bayern comes on Tuesday for the first leg in the Champions League round of 16.
Wissam Ben Yedder scored twice for Monaco. His blocked shot rebounded for Aleksandr Golovin to beat PSG goalkeeper Gianluigi Donnarumma in the fourth minute.
Ben Yedder doubled the lead in the 18th as Monaco pressed high up the pitch. Krepin Diatta dispossessed El Chadaille Bitshiabu and Ben Yedder buried an angled strike into the far corner.
Teenage midfielder Warren Zaire-Emery pulled one back for PSG by tapping home a low cross from Juan Bernat in the 39th.
But Ben Yedder restored Monaco’s two-goal lead moments before halftime with a curling shot off the post. He tied Reims striker Folarin Balogun as the top scorer in the league with 14.
Donnarumma prevented PSG being in a bigger hole by halftime. He parried a close-range header from Ruben Aguilar and denied Golovin, who was clean through on goal.
Monaco managed the game in the second half and Donnarumma saved a low effort from substitute Takumi Minamino in stoppage time.
The kickoff of the Clermont-Marseille game was delayed by 45 minutes because police used tear gas to stop fighting outside the stadium. As some players struggled to breathe, the referee Ruddy Buquet sent both teams back to the dressing room.
Chile striker Alexis Sanchez gave Marseille the lead in the 44th by converting a penalty after Muhammed Cham raised his arm to deflect a free kick from Ruslan Malinovskyi.
Sanchez added a second goal in the 81st by heading in a rebound after his first attempt was saved by goalkeeper Mory Diaw.