Marseille dropped points for the second time in three games as they wasted a two-goal lead in a 2-2 home draw against lowly Amiens on Friday.
Second-placed Marseille, who lost to Nantes two weeks ago, went ahead with goals by Morgan Sanson and Dimitri Payet but conceded the draw in stoppage time when Saman Ghoddos netted the equaliser shortly after Serhou Guirassy had reduced the arrears.
Marseille manager Andre Villas-Boas was shown a red card at the end of the match for launching a verbal tirade at the referee.
The result left OM on 56 points from 28 games, nine ahead of Stade Rennes who play their game in hand at home against Montpellier on Sunday.
Leaders Paris Saint-Germain, whose trip to Strasbourg on Saturday was postponed amid the coronavirus outbreak, are on 68 points from 27 games.
Sanson opened the scoring on the stroke of half-time with a floating shot from just inside the box after being set up by Kevin Strootman.
Amiens were still in the contest and threatened on several occasions but Payet gave OM some breathing space by doubling the tally in the 56th minute after slaloming through the visitors' defence.
Marseille striker Dario Benedetto played part of the game wearing a swimming cap after being bandaged by the medical staff following a clash of heads with Nicholas Opoku.
Guirassy pulled one back in the 84th minute by converting a penalty after he was fouled in the area by Jordan Amavi.
He came close to equalising two minutes later but his deflection of Aurelien Chedjou's header hit the crossbar but Amiens continued to push and were rewarded six minutes into added time when Ghoddos scored from close range.