It was a bad night for the Reds in Italy, as they lost to Napoli in their first game of the group stage.
Alisson made a goalline block and saved a penalty as the Reds were down by three at the half.
After Victor Osimhen hit the post, Piotr Zielinski was able to score from the spot.
Napoli took a 2-0 lead before Zielinski scored twice in the second half.
In the first half, Joe Gomez struggled to deal with Osimhen and was relieved when he left the field with an injury.
It took just three minutes for his replacement to score on his European debut.
There were a number of chances for the visitors, the best of which was a teasing cross that bounced dangerously off HarveyElliott's knee.
Even though they were sloppy in possession, they were punished by a well-organised Napoli side.
There was no chance of a second-half comeback when Zielinski finished over Alisson from close range to make it a four- goal game and though Luis Diaz came close with a diving headed effort, it was too little, too late.
Arthur Melo came on for his debut late in the second half and Thiago made his return from injury, but it was too little, too late for a win.
They were on the back foot from the beginning.
Osimhen gave them a warning when he rounded Alisson and shot against the post.
Five minutes was all it took for Napoli to take the lead when Zielinski scored from the penalty spot.
The typical side would have been expected to bounce back immediately, but this season they have looked tired, demotivated and out of form.
The result was humiliation as the hosts were ruthless and the Reds made many mistakes.
Osimhen ran the struggling Gomez ragged and Napoli could have scored at least another two goals, were it not for a goalline clearance from Van Dijk and a penalty save from Allison to keep Osimhen from scoring.
Anguissa doubled Napoli's lead in style as a quick one-two ripped apartLiverpool's defence, before Kvaratskhaelia set up Simeone's third.
He sprinted down the tunnel after the whistle blew.
The last time the Reds conceded three goals in the first half of a game was in October of 2014).
Rio Ferdinand was a former Manchester United player.
The second half was better for the Reds, but they were still in control.
Two minutes after the restart, the impressive Zielinski added the fourth and the disappointing six-time European champion didn't get any closer.