Olympiacos put one foot in the Champions League knockout stages after substitute Felipe Pardo scored twice to earn the Greek giants a 2-1 win over 10-man Dinamo Zagreb.
Zagreb looked set to pull off a shock when Armin Hodzic crashed in a first-half headed goal to give them the lead at Karaiskakis Stadium before Kostas Fortounis had a second-half penalty saved for the hosts.
But Pardo spared Fortounis' blushes when he netted within seconds of his introduction as a substitute to level the match and then scored the winner in the final minute to leave Dinamo facing a struggle to qualify from Group F.
Olympiacos are second in the group, level on points with leaders Bayern Munich and six clear of Zagreb and Arsenal, who must win their final two games to stand any chance of progressing.
The win extended Olympiacos' unbeaten run to 10 matches in all competitions, but Marco Silva's men were given a stern test by battling Dinamo, despite Josip Pivaric's late sending off for the visitors.
Amid a cacophony of noise from the home crowd, the game began at a fast pace and Dinamo pressed as they sought to restrict their hosts' time and space on the ball.
The early chances fell the way of the home side and Hernani should have opened the scoring when he connected with Arthur Masuaku's cross, but the Portuguese winger looped his header just over the target.
Just as it looked like Olympiacos were settling into their stride, Pivaric found room down the left wing and sent over a cross that found the unmarked Hodzic, whose header slammed against the underside of the crossbar and down into the net.
The home side looked to hit back before half-time, but their best chance was squandered when Seba broke into the box and opted to fire a shot that Eduardo saved easily, failing to see that Brown Ideye was in a better shooting position and crying out for a cross.
Pajtim Kasami went closer just after the break, driving a powerful shot just over, but they suffered a blow when Alberto Botia limped off with a hamstring injury.
Olympiacos were handed a lifeline when Ideye was brought down by Goncalo Santos' tackle from behind and a penalty was awarded. But Eduardo pulled off a superb one-handed save from Fortounis' spot-kick and the midfielder blazed the rebound over.
Next it was Dinamo's turn for a setback as Hodzic was withdrawn with bruised ribs, but Zoran Mamic's side continued to frustrate their hosts with their dogged performance all over the pitch.
The second half turned when Silva sent on Pardo for Hernani. And, within a minute, the Colombian winger was gifted a chance following Ideye's neat turn and pass that he tucked into the corner of the net.
Dinamo's evening got worse when Pivaric clumsily brought down Pardo and was shown a second yellow card by referee Antonio Mateu Lahoz.
The sending off left the visitors exposed in the closing stages and Pardo secured all three points with a coolly taken finish inside the penalty area to spark celebrations in Piraeus.
