Olympiacos, who beat Leverkusen in the league stage at home last month, were again impressive but were undone by Schick's quick-fire brace midway through the second half.

"In the first half it was a difficult match, Olympiacos pressed us with plenty of tempo and made things very complicated for us," Schick told DAZN.

"In the second half we improved a couple of things, scored two goals and got an important win."

Leverkusen's win puts them in the driver's seat ahead of next week's return leg in Germany, with the winners of this tie set to face either Arsenal or Bayern Munich in the last 16.

Wednesday's victory was remarkably Leverkusen's first away win in the knockout stage of the competition in their history.

It was also just their second victory in the knockout phase in 13 games dating back to the 2002 final, lost 2-1 to Real Madrid at Hampden Park.

Leverkusen have won six and drawn one of seven matches in all competitions since losing 2-0 to Olympiacos in January.

In the lead-up to the match, Greek media reported Olympiacos owner Evangelos Marinakis, the billionaire shipping magnate who also owns Premier League side Nottingham Forest, promised players a "record" bonus should they make it past Leverkusen.

As if spurred on, the hosts were brilliant early, pinning the Germans back in their own half in a breathless opening 25 minutes.

Leverkusen absorbed the pressure before going close on 28 minutes when Ibrahim Maza forced home goalkeeper Konstantinos Tzolakis into an acrobatic save.

Olympiacos forward Ayoub El Kaabi turned the ball in from a free-kick just before half-time but VAR found teammate Mehdi Taremi, who was offside, had touched the ball, ruling out the goal.

The hosts once again pinned the visitors back after the interval but Leverkusen took their chance to hit on the break on the hour mark.

Ernest Poku won the ball in his own half and advanced goalwards before threading a superb pass to Schick, who guided his strike into the bottom corner.

"I don't really remember the situation -- it was intuition, my movement," Schick said. "I was one-on-one with the 'keeper, I stayed calm -- it was a good goal."

The stunned hosts were unpicked again just three minutes later when Alex Grimaldo swung in a pinpoint corner which Schick headed home to put Leverkusen in a commanding position.