Liverpool manager Jurgen Klopp says his side only have themselves to blame after a late winner from Lorenzo Insigne gave Napoli victory in their Champions League group game in Italy.
Napoli dominated the second half as substitute Dries Mertens also deflected an effort on to the crossbar.
The hosts had the better chances throughout as Fabian Ruiz and Arkadiusz Milik had shots saved by Liverpool goalkeeper Alisson.
“We have to blame ourselves, that’s how it is,” said Klopp.
Liverpool’s best effort came via Mohamed Salah, who shot wide after the break, but Klopp’s side failed to record a single effort on target in Italy.
Home goalkeeper David Ospina reacted quickly to prevent Sadio Mane and Salah running on to throughballs late on.
But Napoli winger Jose Callejon’s volley was also kept out later in the second half.
“There’s no problem, the boys did a brilliant job tonight,” added Klopp. “They tried everything and were really busy, but not smart enough or calm enough in the right moments.
“When that happens, you lose football games.”
Liverpool’s defence eventually unlocked
Liverpool thought they had weathered a dangerous spell early in the second half when Napoli came close through Milik and Ruiz.
Callejon had also threatened but he was caught offside as he sprinted away down the right before Alisson produced a fine save to deny him from close range.
Liverpool calmed things down, sending throughballs to Mane and Salah as they tried to silence a hostile crowd in Naples.
But they came under pressure again when Mertens and Piotr Zielinski were introduced with 20 minutes to go.
Klopp brought on defensive midfielder Fabinho to try to add more stability but as Liverpool pressed for a winner, Napoli took advantage with a sweeping move down the right to set up Insigne’s winner.
Centre-back pairing Joe Gomez and Virgil van Dijk had been Liverpool’s standout performers before the break, but they were forced deeper into their own half as the match went on.
Insigne’s goal was just the sixth conceded by the pair in their eighth appearance alongside each other.
Disappointment for Keita
Klopp made just one change to the side that drew 1-1 with Chelsea in the Premier League on Saturday as Naby Keita replaced Jordan Henderson in midfield.
Keita, who joined from RB Leipzig for £48m this summer, was making his first appearance in the Champions League for Liverpool but it came to a premature end when he was taken off on a stretcher after just 19 minutes.
He looked in some distress, appearing to point to his lower back as he received treatment on the pitch and was later taken to hospital for “precautionary health checks“.
The 23-year-old had struggled to settle into the game before falling to the ground without contact.
He had made just seven passes and lost possession five times before his evening came to an end but, after his promising displays throughout pre-season, Liverpool fans will hope the injury is not too serious.