Jürgen Klopp said his side “lost the plot” in in a shock 3-0 defeat to Atalanta in the first leg of the Europa League quarter-final.
Former West Ham striker Gianluca Scamacca scored a brace before Mario Pasalic added a third, leaving Liverpool with much to do in the second leg.
Liverpool were hoping to seal their 250th European win in all competitions.
But instead, they suffered their first home defeat in all competitions since Real Madrid beat them 5-2 in the Champions League in February 2023
Klopp said: “It was just a really bad game, oh my God.
“We deserved to lose, and we must feel that now. The boys have this night to feel bad about it.
“Then we have to build up again for Crystal Palace. Congratulations, Atalanta, really well done.”
Asked why his team performed how they did, Klopp quickly praised Atalanta for their tactical discipline.
“Atalanta causes many teams problems with the way they defend.
“I cannot remember a situation where they outplayed us, but they won the ball and went from there.
“You need a lot of tactical discipline to do what they did. They man-marked all over the pitch.
“Man-marking is uncomfortable when you are not on top of your game.
“If you are in a better playing mood than we were tonight, then you can cause massive problems. We suffered from the way they defended.”
Liverpool will have to score at least three goals when they travel to the Gewiss Stadium if they want to stand any chance of progressing into the semi-final.
However, Klopp was focused on galvanising his squad for Sunday’s crucial clash in the Premier League title race.
“I’m not in the mood to think about the game in a week’s time. We have another game in between,” he said.
“This isn’t the time for having a big mouth about what we will do there. This was a low point for us performance wise tonight.”
All focus for Liverpool is now on their return to league action on Sunday, where they will face Crystal Palace at Anfied before they travel to Bergamo to face Atalanta just four days later.
