A stoppage time goal by late substitute Ahmed Hassan gave Olympiakos a 1-0 win over 1993 European Cup winner Olympique Marseille in their Champions League Group C match in Piraeus on Wednesday.
Hassan, who came on for Giorgos Masouras in the 84th minute, headed home an inch-perfect cross by former Marseille forward Mathieu Valbuena after a dominant Olympiakos had missed a string of chances.
In a dour first half, Yann M'Vila volleyed over the bar and Youssef El-Arabi had a close-range shot blocked for the home side, while Florian Thauvin fired just wide at the other end.
Olympiakos had a goal scrapped for offside after a VAR check in the 52nd minute, with Masouras sweeping in a rebound after Marseille keeper Steve Mandanda parried Valbuena's stinging low shot.
Lazar Randjelovic hit the post for Olympiakos in the 69th minute before the outstanding Mandanda palmed away a Valbuena volley from seven meters.
When the game seemed to be heading for a goalless stalemate, Hassan stepped up and beat Mandanda with an unstoppable downward header into the bottom left corner to give the Greek side a well-deserved win.