- Portugal defender Jose Fonte, who turns 37 later this month, scored the winner for Lille with a bullet header just before half-time against Bordeaux.
PARIS: Paris Saint-Germain surrendered top spot in Ligue 1 after losing 1-0 at home to Lyon on Sunday but potentially suffered a more devastating blow as an anguished Neymar was stretchered off with an ankle injury.
Tino Kadewere's first-half goal secured Lyon a seventh win in eight matches as they moved level with Lille, who took over first place earlier in the day following a 2-1 home victory over Bordeaux.
PSG dropped to third after losing for the fourth time in 14 games this season, but the far greater concern will be the health of Neymar after his ankle appeared to twist awkwardly under a challenge from Thiago Mendes in stoppage time.
The Lyon midfielder was sent off for the tackle following a VAR review while a distraught Neymar, in considerable pain, was taken off on a stretcher having immediately signalled for medical assistance.
"He's with the physio and the doctors and we have to wait for the tests tomorrow (Monday)," PSG coach Thomas Tuchel told French broadcaster Telefoot.
Lyon's first win away to PSG since October 2007, the last season they won the Ligue 1 crown, provided fresh hope of a genuine title race this term with the top five teams separated by just three points.
"We defended well, we destroyed their strength, and then played well enough in attack to score at least once," said Lyon coach Rudi Garcia.
PSG trail the leading duo by a point with Marseille, who have two games in hand on their rivals, another point back in fourth alongside Montpellier.
"Losing top spot doesn't worry me. But we didn't have the right approach and I have a problem with that," said Tuchel.
"We were never mentally ready to play this match. We were shot mentally. We never found our rhythm either. We didn't play with enough concentration or discipline. "It was a big step backwards after the last match. I'm surprised. I was expecting a very high level."
With Kylian Mbappe rested from the start, Moise Kean partnered Neymar in attack following the Brazilian's hat-trick in the midweek 5-1 Champions League win against Istanbul Basaksehir -- a game that was completed 24 hours later than planned after an unprecedented anti-racism protest.
Kimpembe error punished
However it was Lyon, without any European commitments this season, who took the lead on 35 minutes after a loose pass under pressure from PSG captain Presnel Kimpembe.
Karl Toko Ekambi collected the ball in the PSG half and immediately picked out Kadewere who steadied himself before sliding low beyond Keylor Navas for the Zimbabwe international's fifth goal of the campaign.
After Navas kept out an attempt from Lyon substitute Bruno Guimaraes, Mbappe had a late chance to rescue a point for PSG but shot wide from the edge of the area in time added on before Neymar's unwelcome injury.
Portugal defender Jose Fonte, who turns 37 later this month, scored the winner for Lille with a bullet header just before half-time against Bordeaux.
Jonathan Bamba's exquisite curling strike gave Lille the lead on 16 minutes at the Stade Pierre-Mauroy before Toma Basic levelled from a Hatem Ben Arfa corner.
Lille travel to bottom side Dijon in midweek before the visit of defending champions PSG next Sunday in what could be a defining week for a club chasing a first league title since 2011.
"I don't think we can fight with Paris for the title.
We need to fight to pick up points and stay at the top," said Lille coach Christophe Galtier, keen to temper expectations.