Liverpool were deservedly defeated by Napoli at Stadio San Paolo, as Lorenzo Insigne saw the visitors make the most of their superiority late on.
The Reds' front three of Firmino, Mane and Mohamed Salah were particularly disappointing, as they had very little impact on the match.
Klopp accepts a draw would have been more than they deserved and feels the formation Liverpool used was a mistake.
Speaking to BT Sport, Klopp said: "We had our moments, but too often the formation was not right or we moved in the wrong spaces.
"The job of the midfield three was nearly impossible. You have to stay calm in a situation like that, but we were too hectic with the ball.
"You have to prepare it [the system] well. You can't just hope something will happen.
"Sometimes Bobby [Firmino] ran too long with the ball, or Sadio [Mane] ran too long. When that happens, you cannot produce.
"The midfielders or the full-backs tried to go forward, but we lost the ball and had to go back in the other direction.
"We had good moments, but not enough. A 0-0 away from home is OK, but we made a tactical mistake before their goal.
"That's the second time this season that we have conceded a goal like that, then they were on their bikes, the atmosphere was there because we let them do what they did. That's it, the story of the game.
"We want to play better than we did, but even if we don't play brilliantly, we want a result. We weren't as good as we could be. We have to blame ourselves."
An apparent back injury forced Naby Keita off in the first half, but Klopp was unable to offer any update.