Lyon was dealt another blow in the race for a Champions League spot as the seven-time French champions were held to a 1-1 draw at relegation-threatened Brest on Monday.
In a match of few chances, Czech midfielder Mario Licka scored the equalizer in the 76th minute as Claude Puel's team faltered again just five days after an humiliating 4-0 loss at Auxerre.
Brazilian midfielder Ederson had opened the scoring for Lyon in the 15th minute.
Third-placed Lyon now leads PSG by two points with two rounds remaining this season but PSG has a game in hand to play at Bordeaux on Wednesday.
"We need to grit our teeth and wait for PSG's result in Bordeaux," Lyon president Jean-Michel Aulas said. "This is a very difficult and very close end to the championship season."
Brest is 15th just two points above the relegation zone.
Lyon dominated possession in the early stages and was rewarded when Ederson, left unmarked at the near post, headed home Miralem Pjanic's corner from the left.
Kim Kallstrom could have extended his team's lead in the next minute after Brest failed to clear the ball properly but the Swedish midfielder's low shot from 20 yards ended just wide.
Lyon goalkeeper Hugo Lloris made a save in the 49th minute when he denied Bruno Grougi's effort from close range. But the France keeper was helpless when Licka fired a long-range half-volley in the top left corner only seven minutes after coming on as a substitute.
"We can't be satisfied with this draw, we were pushed back too often," Lyon defender Aly Cissokho said.
League leader Lille can virtually seal the title if it beats Sochaux on Wednesday. The Northern side leads defending champion Marseille by three points and would then have a six-point lead and a much better goal difference.
Lille beat holder Paris Saint-Germain 1-0 in the French Cup final last weekend to win its first trophy since 1955.