The red shirts were carved open time and time again, particularly in the first half, and only some wayward finishing – including a missed penalty from Napoli striker Victor Oshimen – kept the scoreline to a semi-respectable 3-0 at half time.
An early penalty from Piotr Zieliński after a James Milner handball set the tone for the match, as wave after wave of blue shirts descended on Alisson’s goal.
Trent Alexander-Arnold – who has endured a particularly torrid start to the season – and Joe Gomez were caught out on numerous occasions in the first half, before André-Frank Zambo Anguissa finally got Napoli’s second, slotting the ball past Alisson after a smart exchange with Zielinski.
Then just before the break, Champions League debutant Giovanni Simeone, who had come on as a substitute for Oshimen, was gifted an easy tap-in after being found completely unmarked in front of goal by Khvicha Kvaratskhelia.
If Liverpool manager Jurgen Klopp had hoped the half-time break would allow his team a chance to regroup and come out fighting in the second half, he was sorely mistaken.
Within two minutes of the restart, Napoli had made it 4-0 as Zielinkski got his second, prodding home the rebound after Alisson had saved his initial effort.
It was almost too much for Klopp to bear, as he pulled his cap down from his head to cover his eyes from the horror he was watching.
Liverpool did get one back just a couple of minutes later after a mistake in the Napoli midfield had gifted Luis Díaz possession, allowing the Colombian to bend a smart finish into the bottom corner.
In truth, there was never any chance or sign of a toothless Liverpool mounting a comeback on what Klopp described as a “really tough” night for the club.
“[It’s] tough to take,” the German told BT Sport. “I would say not that difficult to explain when you saw the game. First of all, Napoli played a really good game and we didn’t, that is the first explanation for the defeat.
“It looks a little bit like we have to reinvent ourselves. There are a lot of things lacking, not in all the games, but now the fun part is we have to do it in the middle of a Premier League season and a Champions League campaign.
“In three days’ time, we play Wolves and, when they saw the game tonight, they cannot stop laughing, probably, and think: ‘Oh my god, that’s a perfect moment [to play Liverpool],’ but we have to try to find a setup to be much better in pretty much everything.”
Liverpool currently sits seventh in the Premier League with just two wins from its opening six matches.
With two successive home matches coming up against Wolves and Ajax, nothing less than six points and a vast improvement in performance will do for a team desperate to get back on track.