Olympique de Marseille's second place in Ligue 1 was under threat on Saturday as they slumped to a 2-1 home defeat by AC Ajaccio.
Dimitri Payet's 100th league goal meant little in the end as it was quickly followed by Bevic Moussiti-Oko's equaliser and Leonardi Balerdi's own goal.
The result left OM on 23 points from 10 games, two behind leaders Paris St Germain who travel to Stade de Reims later on Saturday.
Third-placed Lorient will leapfrog them into second place if they beat Brest and fourth-placed RC Lens will also move ahead if they grab all three points in the northern derby at Lille on Sunday.
At the Stade Velodrome, Payet opened the scoring with a spot kick after a Cedric Avinel handball in the 15th minute.
Ten minutes later, however, Moussiti-Oko outpaced the Marseille defence to beat Ruben Blanco with a left-footed effort.
The visitors went ahead two minutes into the second half when Balerdi deflected Youssouf Kone's cross into his own net and Marseille's only clear chance then came in the 55th minute when Oumar Gonzalez almost scored an own goal, too.