Rafael Benitez condemned his Liverpool side's approach to their shattering 2-0 Champions League defeat by Fiorentina.
The Spaniard seemed to suggest it was the worst European performance under his Anfield management.
Two first-half goals from teenage striker Stevan Jovetic stunned Liverpool, and even with an improved display after break, the damage had already been done.
Benitez said: "In that first-half we did not play well, there were too many mistakes and problems. We did improve, but it was not enough.
"Our mentality in that opening period was just not right, we were bad all over the pitch and I cannot really recall a performance like that.
"They were on top of us all the time, we played badly and they were just better than us."
Liverpool went behind when Jovetic broke the offside trap with Adrian Mutu deemed not to be interfering with play.
"It is the new law, and another mistake by us," Benitez said.
"If a player is in such a position he is offside, and it makes it difficult for defenders who are distracted by him. But the law says the other player coming from deep is fine, he can go through. Just another error by us."
Jovetic took advantage of poor defending on the near post to claim his second, and Benitez was also critical of the tackling and pressing from his team.
He said: "I was not only disappointed with the challenging in midfield but all over the pitch.
"But they did not produce anything we did not expect. We had watched them, we knew about Jovetic, there was nothing new out there that surprised us. But we still played badly.
"We now have Chelsea away at the weekend in an important Premier League game. I believe you will see a different Liverpool in that match, a totally different performance with a different mentality.
"Then we have Lyon home and away in this group, they are the leaders and it means we have to now win them both.
"We certainly will not be as bad again. If you make too many mistakes against such sides, you will be punished. It is very simple.
"Mentally we will have better days than this. We did improve, but we needed to score early in the second-half. We had the chances but we failed to take them."
Fiorentina coach Cesare Prandelli was delighted with his own team.
The former Juventus player said: "We were fantastic, that is the best performance I have seen by a Fiorentina side in the four years I have been in charge.
"Liverpool did not play well, but that was because of the performance of my team. We were outstanding.
"Especially in that first-half when we were just fantastic. The pressure we put Liverpool under all over the pitch was wonderful to watch.
"But although we played well, I believe we can still improve, and we will have to if we are to qualify from this group.
"To have beaten such a great team with such brilliant players was an achievement, but we must not waste this and we now need to keep winning in this group.
"I will now rotate my squad for the weekend, this team is not just 11 players, but a real squad. Everyone has to play their part.
"I was delighted with Jovetic. I have always said he has great talent, but last season maybe he did not play for the team, now is working for everyone else and he is gaining his rewards."