Omer Toprak and Bayer Leverkusen know it will be tough to salvage their Champions League last-16 tie after conceding four goals against Atletico Madrid.
It was a night to forget for Leverkusen on Tuesday as the German hosts lost the opening leg 4-2 at home to Atletico.
Leverkusen trailed 2-0 heading into the second half at BayArena and while Karim Bellarabi's strike and Stefan Savic's own goal prompted a late onslaught, Atletico were always in control thanks to Kevin Gameiro's contentious penalty and a Fernando Torres header.
Speaking afterwards, Toprak said: "In the first half, we played really badly. We have invited Atletico to score.
"In the second half, we played better. But the result is not good."
Atletico stormed out of the blocks thanks to Saul's stunning 17th-minute solo effort, before Antoine Griezmann doubled the lead eight minutes later.
Bellarabi gave Leverkusen some hope when he pulled a goal back three minutes into the second half, only for Gameiro to restore Atletico's two-goal buffer approaching the hour-mark.
When Savic turned the ball into his own net in the 67th minute, Leverkusen pushed more numbers forward but Atletico were dangerous on the counter-attack and Torres added another away goal with four minutes remaining.
"We kept believing we could get back into the game, but you have to admit Atletico deserved the win today," Bellarabi told Sky Germany.
"We didn't really get into the game in the first half. We had a few more chances to score, but it was a difficult game for us.
"We're not in a great position, but we'll keep going. We know it'll be tough, though."