Marcelo Bielsa's side have not won away from the Stade Velodrome since October and fell behind in the 27th minute as Ola Toivonen put Rennes ahead with a volley into the bottom-left corner.
But the visitors secured a point on the hour mark when winger Lucas Ocampos marked his debut by converting Dimitri Payet's corner.
Yet the contest ended in disappointing fashion for Marseille as midfielder Mario Lemina was sent off for striking Toivonen in the groin five minutes from time, leaving the Provence club to settle for a point.
Second-placed Marseille are now a point behind Lyon and will be hoping for a draw between the league leaders and defending champions Paris Saint-Germain in a crucial fixture on Sunday.
At the other end of the table, Caen's surge continued with a fourth straight win, the Normandy outfit overcoming Toulouse 2-0 to go four points clear of the drop zone.
Sloan Privat opened the scoring in the 17th minute before Julien Feret made sure of the points with a 72nd-minute penalty.
Coupe de la Ligue finalists Bastia and fellow strugglers Lorient are also four clear of danger following much-needed victories.
Bastia prevailed 2-0 at home to bottom club Metz - who had defender Guido Milan dismissed - while Lorient came from behind with three second-half goals in a 3-1 triumph at Reims.
Wahbi Khazri's spectacular 11th-minute effort was enough to see Bordeaux edge third-bottom Evian 1-0. The Tunisia international surged towards the edge of the area before powering a thunderous shot into the top-right corner.
Elsewhere, goals from Nolan Roux and Marcos Lopes helped Lille to a 2-1 win at Montpellier.
