The Reds were stunned in Naples tonight, with Lorenzo Insigne netting a 90th-minute goal in a 1-0 win.
Liverpool struggled to get going against Napoli, with the Serie A side impressing against Klopp’s men.
The Reds, who were sloppy all night, were also handed a major blow with Naby Keita being stretchered off after 15 minutes.
And Klopp says Liverpool struggled to deal with Napoli’s free-flowing play, claiming his side weren’t smart enough against the Italian giants.
“We had our moments, but too often the formation was not right or we moved in the wrong spaces,” said Klopp.
“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.
“They were on their bikes. We let them do what they did.
“We had good moments, but not enough. A 0-0 away from home is OK, but we made a mistake before their goal.
“That’s the second time this season that we have conceded a goal like that.
“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.
“It was intense, but we caused the intensity of the game ourselves.
“It was an interesting looking group before we started and it’s still interesting now. We want to play better than we did tonight, but even if we don’t play brilliantly, we want a result.
“Tonight we just weren’t good enough, we weren’t as good as we could be. The defeat is deserved.
“The boys did so far a brilliant job but it wasn’t meant to be tonight. We weren’t quick enough, we weren’t smart enough.”
On Keita’s injury, Klopp added: “Back problem, that’s what I heard. We don’t know anything yet. We will have to wait.”
It’s Liverpool’s second defeat of the season, after their Carabao Cup defeat against Chelsea last week.
Liverpool return to Premier League action on Sunday afternoon, with the Reds facing Manchester City in a top of the table showdown (4:30pm kick off).
A win for Klopp’s men would send the Reds to the top of the Premier League.