The Reds took to the Stadio San Paolo looking to add to the three points picked up in the group stage opener at home to Paris Saint-Germain.
But a goal from Lorenzo Insigne ensured a 1-0 defeat for Liverpool, serving as a major setback for the visitors.
“I’m not 100 percent sure why [we were poor] but it is clear that we were.
“The timing for our defensive movements were not good enough, we didn’t close the space in the right moment, we didn’t react in the right situation. And so they could play through.
“We didn’t create a lot of chances. Second half was not good enough.
“It’s always a bad sign when you have to say your goalkeeper was your best player, but it was obvious tonight.
“A big part of that performance is my fault. I need one night to watch the game again, but it looked not like it should have looked.”
The manager also discussed Naby Keita‘s injury, but could offer little, saying “I heard it’s a back problem, but we don’t know exactly—we have to wait.”