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Sambou Yatabare was next to test his luck with a long-range effort, but his strike sailed over the bar.
Soon after the restart, Roberto was called into action action to keep out Markovic's volley and minutes later he saved a fierce strike from Enzo Perez.
Substitute Filip Djuricic attempted to beat the Olympiacos keeper but his powerful effort was saved.
With just two minutes of the match left to play, Djuricic tried to poke the ball home from close range but Roberto again came to his teams rescue and earn them three valuable points.