Andre Ayew rose to head home a corner deep into injury time tonight as Marseille beat Internazionale 1-0 in the first leg of their Champions League last-16 match.
Inter, the 2010 champion, grew in confidence as the second half wore on, but struggled to carve out clear chances against a well-organized Marseille team that lacked invention and a cutting edge up front.
Claudio Ranieri's team looked to have done enough to secure a draw, but Ayew timed his run perfectly in the third minute of added time to head the ball past goalkeeper Julio Cesar's outstretched hand to condemn Ranieri's side to its sixth defeat in the past seven games.
Diego Forlan had Inter's best opportunity early in the match when he forced goalkeeper Steve Mandanda to tip the ball over the crossbar from close range.
The return leg is at Inter on March 13.
Marseille was without top scorer Loic Remy with a thigh injury, but midfielder Alou Diarra started after shaking off a toe problem. Brazilian Brandao took up a lone striker's role with Mathieu Valbuena behind him as playmaker.
Both sides started with a near-identical shape in a 4-2-3-1 formation.
Under-fire Inter coach Ranieri gave Forlan his European debut for the club — the Uruguay striker was ineligible for the group stage — and he was supported by Wesley Sneijder in a revamped attack. Forwards Diego Milito and Giampaolo Pazzini were on the bench.
Marseille attacked aggressively from the outset, keen to test a defense that had leaked 15 goals in the last six games, five of which were defeats, and midfielder Benoit Cheyrou saw his speculative shot deflected for a corner.
Inter tried to sit back and soak up pressure, happy to hit the French side on the break, but veteran midfielder Dejan Stankovic betrayed his side's early nerves when he hit a routine short pass into touch, rather than to teammate Mauro Zarate standing five yards away from him.
Despite Marseille's bright start, Inter had the first shot on target in the 11th minute when Forlan forced goalkeeper Steve Mandanda into an excellent reflex save after running onto Esteban Cambiasso's pinpoint cross from the left.
Marseille remained in control, however, and midway through the first half Valbuena caught Lucio napping as he tried to casually dribble out of defense. Valbuena stole the ball off Lucio's toe, but then just failed to get it over to Brandao.
Valbuena often dropped deep or shuffled wide to support wingers Andre Ayew and Morgan Amalfitano, making it increasingly hard for Inter's defense to predict his runs.
Marseille should have scored in the 30th. Center half Nicolas N'Koulou ran onto Valbuena's curling freekick and clipped the ball straight onto the leg of teammate Souleymane Diawara, rather than toward goal.
Inter almost punished Marseille for that wasted chance just moments later, when Cambiasso pulled the ball back to the unmarked Zarate, but his shot lacked power and was comfortably smothered by Mandanda.
Marseille right back Cesar Azpilicueta tested keeper Julio Cesar with a dipping shot from 15 yards early in the second half, but Inter pushed up more and Marseille found itself trying to launch attacks from deep.
Ranieri seemed increasingly content to settle for a draw, replacing Zarate with Joel Obi midway through the second half, even though Zarate was Inter's most lively player along with Cambiasso.
With both sides hitting stray passes, the play became more scrappy with players from both teams overlooking simple passes as they tried to make the difference themselves.
Forlan embarked on a swerving run that saw him skip past four Marseille players, turn back on himself and lose the ball, while Marseille midfielder Benoit Cheyrou's ambitious chipped pass into the box was easily headed away, with Ayew screaming for a pass right next to him.
Stankovic then scuffed a weak shot straight at Mandanda from close range in the 74th after Sneijder curled a dangerous free kick into the box.
And it got worse for Inter in injury time when Ayew, who had gone close with two headers shortly before, won the match for Marseille and gave his team a slim advantage heading into the second leg.