With a victory, Igor Tudor’s second-place team might have closed the deficit to PSG to four points before the defending champions’ match against Lyon on Sunday.
However, Marseille lost for the third time in five league games and now faces a possible overtaking by Lens when they travel to Montpellier on Saturday.
Tudor said, “Today we weren’t good enough to win.
“The international break has been quite costly for us. There were too many exhausted players both physically and mentally.
“We only had one training session together so I knew it would be tough.”
Following an outstanding burst by Wahbi Khazri, Arnaud Nordin completed a swift counterattack to give mid-table Montpellier a lead in the 12th minute.
Before to halftime, Matteo Guendouzi scored from the penalty spot after Marseille was called for a handball.
However, OM failed to generate any offense, and halfway through the second half, Khazri came dangerously near to giving Montpellier the victory when home goalkeeper Ruben Blanco denied him.
After PSG’s shocking home loss to Rennes before the international break, Marseille dominated possession late in the game but was unable to score, which would have given them renewed hope of winning their first league championship since 2010.