|Bordeaux's Guinean forward Francois Kamano (right) controls the ball past Olympique de Marseille's French midfielder Florian Thauvin (left) during the French L1 football match. (NICOLAS TUCAT/AFP)|
Nicolas de Preville put Bordeaux ahead in only the third minute with an excellent individual goal, but after a largely lifeless display, Marseille snatched a point at the death through Sanson's low finish.
Jocelyn Gourvennec's Bordeaux have now followed a 14-match unbeaten streak with a six-game winless run in Ligue 1, while Marseille stay fourth, a point behind Lyon.
"In the first half we lacked technical accuracy, we gave the ball away too much," Sanson told Canal+.
"The point is very important, we open up a gap over them. That's a point that will count at the end (of the season)."
De Preville got the hosts off to a flying start as he nipped in to beat Sanson to the ball in midfield, before racing clear and curling an unstoppable finish in off the far post to score his first goal for the club.
Dimitri Payet looked lively for Marseille and had a shot blocked, but Bordeaux could have moved further clear when Younousse Sankhare fired inches over the bar.
The away side were slightly improved after half-time, with Florian Thauvin volleying into the side netting and Kostas Mitroglou also firing wide.
Bordeaux were the better side, though, and with a little more composure up front they could have wrapped up the points as counter-attacks often broke down with either ill-judged shots or poor passes.
It was a sequence of terrible defending that gifted Rudi Garcia's Marseille a leveller in the final minute of injury time, as the hosts wasted multiple chances to clear a simple free-kick into the box and Sanson fired through home goalkeeper Benoit Costil from close range.
LYON STRUGGLE WITHOUT FEKIR
Lyon's four-match winning streak in Ligue 1 came to an end without captain Fekir as they were held to a 0-0 home draw by Montpellier.
Bruno Genesio's men slipped to nine points adrift of league leaders Paris Saint-Germain after a disappointing performance.
The hosts went into the game in a rich vein of form, having scored 21 goals in six league matches since a 2-0 defeat at PSG in September.
But they had to make do without top scorer Fekir, with the 24-year-old suspended after picking up his third yellow card of the campaign for his celebration after scoring the final goal in the 5-0 derby thrashing of Saint-Etienne.
"We know that we have a good team, but when we miss a player of the quality of Nabil Fekir, it's obviously a big problem. He is very important for us," said Lyon centre-back Marcelo.
Earlier on Sunday, Nice's miserable start to the season continued as Ronny Rodelin scored an injury-time equaliser for Caen in a 1-1 draw.
Pierre Lees-Melou had given Nice a first-half lead, but with Mario Balotelli suspended, Lucien Favre's men failed to build on that advantage and are now just two points clear of the bottom two.
PSG extended their lead at the top of the table over Monaco to six points by beating Nantes 4-1 on Saturday, with Edinson Cavani scoring a brace.
Defending champions Monaco dropped two points in a 1-1 draw at newly-promoted Amiens on Friday, despite a second-half equaliser from Stevan Jovetic.
French Ligue 1 results:
Caen 1 Nice 1
Lyon 0 Montpellier 0
Bordeaux 1 Marseille 1