Florian Thauvin and Marseille suffered a blow to their European hopes as they were beaten 1-0 at Saint-Etienne on Sunday while Les Verts made top-flight survival a mathematical certainty.
Marseille had lost just one of their previous eight top-flight games after showing marked improvement under new coach Jorge Sampaoli. Lens — directly below OM in sixth — had lost their derby to Lille on Friday night while seventh-placed Rennes, the other contenders for fifth place, face a tough test at home to Paris Saint-Germain in Sunday's evening kick-off, so a trip to Saint-Etienne represented an opportunity to seize the initiative.
The record French champions have struggled at home this season, taking six fewer points at their Stade Geoffroy-Guichard than they have on the road, but Claude Puel's had won four of their last seven L1 games, and they made life difficult for the visitors from the off.
Steve Mandanda pawed away a Wahbi Khazri strike from distance (18') and then another from the Tunisia international from an acute angle (19') before an injury to Harold Moukoudi forced Puel into an unexpected change of plans in his backline (27').
Not that Moukoudi's replacement, Timothée Kolodziejczak, was troubled much. It was Mandanda who was the busiest man on the pitch, leaping to keep out a curling Denis Bouanga effort (39'), before he was finally beaten: Khazri picked out Arnaud Nordin at the back post, and having stepped round Leonardo Balerdi's challenge, he beat Mandanda from close range (43').
Clearly shaken up by Sampaoli at half-time, Marseille responded. Luis Henrique's cross from the left reached Thauvin, but he found Miguel Trauco in his path, and when the ball ricocheted to Arkadiusz Milik, the Polish striker was closed down by the tenacious Mathieu Debuchy before he could fire goalwards (53').
Dimitri Payet came much closer when rattling the right-hand post of Etienne Green with a trademark free-kick (56'); Green then superbly kept out a Luis Henrique shot as OM showed the sort of character that had earned them eight points from losing positions during Sampaoli's short tenure (65').
With the visitors pressing, space opened up for Saint-Etienne, and Adil Aouchiche should have taken advantage after Romain Hamouma's run had split OM, but the youngster dallied on the ball and was robbed by the industrious Thauvin (73').
Green and Mandanda then traded saves: the former denying Payet (77'), the latter keeping out Hamouma after he had skipped away from Alvaro Gonzalez (83'), but the France international's efforts were in vain as the hosts took the points.
THE PLAYER: Etienne Green
The youngster may have found himself between the posts in fortuitous circumstances in this season finale, but he has taken the opportunity with both gloved hands, and again showed his potential here. Though Mandanda made more saves, Green kept Marseille at bay to earn his side the points, and deserved the stroke of fortune he enjoyed with Payet hitting the woodwork.
THE STAT: 41
This is the first time since the 1979/80 L1 season 41 years ago that Saint-Etienne have won both games in the campaign against Marseille.