Brown Ideye scored a late goal to give Olympiacos a priceless 1-0 away win at Dinamo Zagreb in Champions League Group F.
The striker chased down a nothing ball from Dimitris Siovas and squeezed the ball home past Eduardo from a tight angle with just 12 minutes left.
Dinamo had missed the game's best chances earlier in the second half with their captain Domagoj Antolic and Marko Rog both hitting the post.
But they could not break the deadlock and succumbed to their first defeat on home soil since a 5-1 reverse to Red Bull Salzburg in the Europa League last November.
It was smash and grab for Olympiacos, who were mostly restricted to shots from distance but made their best opening count when Ideye scored for the third match in a row to snatch the points.
The Greeks now look well placed to qualify from Group F with six points from their three fixtures and a home clash with the Croatians to follow.
Dinamo may argue they deserved more, having dominated the opening stages, with Rog particularly threatening. The winger did brilliantly down the left to beat his man but Siovas cleared for Olympiacos with nobody attacking the cross.
El Arbi Soudani then attacked down the opposite wing and cut inside to open up a sight of goal, only to waste the chance and shoot well wide, before the Algerian set up Junior Fernandes, who shot straight at Dinamo goalkeeper Roberto.
Dinamo then put together the finest move of the match but the flowing attack came to a stuttering end when Soudani picked out Armin Hodzic in the box, but the striker was well marshalled by the determined Olympiacos defence and failed to get a shot away.
Olympiacos were being restricted to shots from distance, with Arthur Masuaku forcing Dinamo keeper Eduardo into his first action of the game on the half hour with a swerving strike from distance, but the goalkeeper was alert to the danger.
Both sides opened up after the cagey first half and Dinamo skipper Antolic should have opened the scoring shortly after the break, but with the hosts suddenly four-on-two, his shot hit the outside of the post.
Olympiacos ought to have compounded that error immediately but Ideye could not convert a low cross from Pardo with Eduardo stranded.
Kostas Fortounis slashed wildly off target from distance as the Greeks committed more men forward in their attacks and Ideye atoned for his earlier miss by scoring a fine solo goal, beating Eduardo from near the byline after chasing down a long pass over the top.
Dinamo threw men forward but could not find a late response and their qualification chances now look slim.
