Marseille stretched their undefeated run at Rennes to seven games on Saturday but a laboured 1-1 draw meant they squandered the chance to go top in France.
Marcelo Bielsa's side are one point behind leaders Lyon who tackle champions and third-placed Paris Saint Germain in the weekend's standout fixture on Sunday.
In a depressing summary of Marseille's afternoon, they finished the game in Brittany with 10 men after Mario Lemina was red-carded in the 83rd minute for a foul on Ola Toivonen.
Swedish striker Toivonen was a thorn in Marseille's side all afternoon.
The 28-year-old gave Rennes the lead after 26 minutes, smartly chesting down a loose ball to score past Steve Mandanda in the visitors' goal.
Marseille were saved when Lucas Ocampos, the Argentine signed on loan from Monaco in the last moments of the transfer window, found the net in the 59th minute after coming on as a half-time substitute.
The winger was handily placed to score from a corner taken by Dimitri Payet.
"The match was equal. We started well without making an impression," said Bielsa, who will be keen to get influential Ghana star Andre Ayew back from the Africa Cup of Nations.
"In the second half of the first period we lost possession. We couldn't attack and we suffered in defence," added Bielsa, whose team are without an away win since October.
"Our attitude was better in the second half as was the team's production. We could have made the most of it after our goal but the red card put the brakes on the way we wanted to play."
PSG can reclaim the top spot on Sunday, but they need to beat current leaders Lyon away from home to do so.
It's a tough assignment for Laurent Blanc's men, but they were boosted by a 1-0 win over Lille in midweek that took them into the French League Cup final.
"It's not a final but it could be the turning point of the season", said midfielder Blaise Matuidi.
"We've got a lot of avenues open to us and we want to do well in all the different competitions."
Lyon are on an eight-match unbeaten run, having only dropped points at Monaco.
But, just as they did in the Principality, Lyon will have to do without their top scorer Alexandre Lacazette (21 league goals).
The French international hasn't played since injuring his thigh in the 2-0 win over Metz last month.
Source: AFP