Liverpool manager Jurgen Klopp has admitted his defence must improve.
The Reds blew a two-goal lead to draw 2-2 with Brighton at Anfield last Saturday.
Speaking prior to Wednesday's clash with Atletico Madrid, Klopp acknowledged his team needed to stop conceding goals.
"We aren't perfect, I know that," Klopp told reporters. "I knew that before. We have to defend situations better, that's absolutely clear and no doubt about that.
"But we had before, I don't know how many clean sheets Ali had already this season. We cannot always make these discussions because of one game.
"You beat United 5-0 and the world is very rosy and then in the next moment you draw 2-2 against Brighton and you have massive problems. It is neither nor. We have to improve, that's what we know.
"Against Brighton, the best way of defending would have been to keep the ball, to play football we played in our good periods, in the first half especially.
"That's what we didn't do and that was my problem. I knew before the game that we would have problems in moments against Brighton because all teams had it so far.
"That's the quality of Brighton; they don't finish those situations off always but against us they did and that's why they deserved a point.
"It has nothing to do with tomorrow, but that we have to defend in general better, we knew that before. We work on that and we better do it tomorrow night because Atletico are a pretty good football team."
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