Despite being under pressure for large parts of the game Ernesto Valverde's men vastly improved in the second half to gain the advantage in the tie
The hosts dominated the first half but failed to find a way past a resilient Greek outfit. David Fuster turned the game on its head with an opportunistic strike early in the second half, enabling his team to then concentrate on seeing the game out.
The hosts started with nine players that were born in South America and their influence was clear as they passed the ball fluidly along the deck. With Villagra bombing foward from right-back it was easy to see why they are the tournament’s top scorers with 23 goals in eight games.
However, Olympiakos possess a mean defence and Metalist were struggling to get in behind.
After 17 minutes Balazs Megyeri was the first goalkeeper to be called into action after a slick move from the hosts. Taison cut in from the left flank and found Jose Sosa who teed up Sebastian Blanco with a backheel. Blanco’s effort was meant for the top corner but flew at a suitable height for Megyeri to save.
Metalist were perhaps guilty of trying to walk the ball through Olympiakos and their next decent chances came when they changed tact.
Sosa bent an enticing cross in from the right which found Jonathan Cristaldo but his header missed the target. Then, before the half-hour mark, Taison clipped a lovely ball over the top for Fininho but the full-back pulled his volley wide from an acute angle.
With the game becoming somewhat ill-tempered towards the end of the half, Ernesto Valverde clearly told his Olympiakos side to concentrate on playing football.
Kevin Mirallas led the charge and he was instrumental in the opening goal five minutes after the restart. Marco Torsiglieri failed to deal with Mirallas’ ball into the box and Fuster capitalised, scissor kicking the ball in from six yards.
The Greek side were almost pegged back moments later as Metalist stepped up the tempo. Edmar found space in the box but his header sailed over the bar from another exquisite Sosa delivery.
Sosa continued to excel down the right and in the 66th minute he beat two men and crossed to the back post. With Megyeri scrambling across the goal it looked like a simple nod into the goal for Taison but the Brazilian somehow missed the target, spurning a golden opportunity to level the game.
The introduction of Marko Devic helped keep the momentum with the Ukrainians but Olympiakos remained resolute at the back.
Metalist's hopes of an equaliser were extinguished when Edmar received his marching orders eight minutes from time for a two-footed challenge on Giannis Maniatis.
Olympiakos' ninth successive clean sheet puts them in the driving seat for next week's decider. Metalist can still rescue the tie however, and will relish the chance to break through the Greeks' defence.