Match ends, Napoli 2, Liverpool 0.
Dries Mertens' penalty and a late Fernando Llorente goal condemned Liverpool to defeat in their Group E Champions League opener against Napoli.
Belgian forward Mertens scored from the penalty spot after Liverpool defender Andy Robertson was judged to have fouled Jose Callejon.
Former Tottenham forward Llorente then capitalised on a mistake from Virgil van Dijk in stoppage-time to roll the ball past Liverpool keeper Adrian.
Jurgen Klopp's side are the first winners of the competition to lose the opening game of the following campaign since AC Milan in 1994.
Referee Felix Brych's decision to award a penalty for Napoli's opener stood after it was looked at by video assistant referee (VAR) officials.
"I'm pretty sure there are different views on that situation but when a player jumps before there is contact then it cannot be a penalty," said Klopp.
"It was very decisive in that moment for sure but we can't change it. As long as human beings make the decisions then there is still potential for [mistakes].
"The rules are like this and we trust in the rules."
Goalkeeper Adrian had earlier made two keys saves for Liverpool, who initially struggled to impose themselves in the intimidating atmosphere of the San Paolo Stadium.
The 32-year-old, deputising for the injured Alisson, twice saved from compatriot Fabian Ruiz during the first period and produced an outstanding point-blank save from Mertens' volley just after the break.
However, unlike the corresponding fixture last season, when Liverpool failed to register a shot on target in their 1-0 defeat, Klopp's side did produce moments of slick football to threaten the hosts.
A flashing Mohamed Salah drive was superbly tipped to safety by Napoli goalkeeper Alex Meret, who also saved Sadio Mane's toe-poked shot with the score at 0-0.
But while Klopp's side have made a blistering start to the Premier League, averaging three goals per game, their failure to exploit several good breaks consigned them to a sixth defeat away from home in their past eight matches in the competition.
Koulibaly snuffs out Liverpool threat
Liverpool's failure to puncture the home defence was largely down to the impressive form of Kalidou Koulibaly.
The Senegal international repeatedly demonstrated why he was been mentioned in dispatches throughout the summer as a target of the Premier League's biggest clubs.
Named the best defender in Serie A last term, the 28-year-old made several key interceptions and dispossessed both Roberto Firmino and Salah in one-versus-one situations.
And he continued in that vein, patrolling behind left-back Mario Rui to snuff out the danger posed by the Egyptian's pace and trickery.
His reading of the game was exemplary throughout, ensuring he was rarely caught out of possession and was able to spring Napoli attacks.
Conservative Liverpool fail to sparkle
Klopp's team lost all three away games in last season's group stage, but overwhelmed teams at Anfield with their pace and energy, and the brilliance of forwards Mane, Salah and Firmino.
Jordan Henderson's searching second-minute pass into the path of Salah seemed a precursor to the sort of dominant attacking display that has served Liverpool so well.
However, on a warm evening in Naples, Klopp's side appeared to take a more conservative approach exemplified by full-backs Robertson and Trent Alexander-Arnold's failure to press forward.
In midfield Fabinho snapped away but their was an absence of sparkle in possession, with Henderson and James Milner delivering solid displays but not the sort of service that Liverpool's attacking triumvirate are accustomed to.
Only goalkeeper Adrian touched the ball less than Salah and Firmino.
And that lack of involvement perhaps also contributed to Mane's indecision, when racing towards goal, with the Senegalese forward over-hitting a pass to Salah that could have put the Egyptian in.
Man of the match - Kalidou Koulibaly (Napoli)
Napoli maintain record against English clubs - the stats
- Napoli have now won five of their six Champions League home games against English opposition (L1 - a 2-4 defeat to Man City in November 2017).
- Liverpool have lost their opening Champions League match of a new campaign for only the second time (P12 W6 D4 L2), and for the first time since a 0-2 defeat to Valencia in September 2002.
- Liverpool had more shots in the opening 22 minutes of this match (five) than they managed through the entirety of this exact fixture in the competition last season (four).
- Liverpool have lost six of their last eight away games in the Champions League (W2), as many as in their previous 25 such matches in the competition.
- Since the start of last season, only Nicolas Tagliafico (six) has received more yellow cards in the Champions League than Liverpool's Andy Robertson (four).
- Napoli striker Dries Mertens has scored more Champions league goals than any other Belgian in the competition (11).
- Since a 2-0 win over Udinese as Borussia Dortmund boss, Liverpool manager Jurgen Klopp has lost on his last five visits to Italian sides in all competitions (P5 W0 D0 L5).
- Napoli striker Fernando Llorente has now scored a Champions League goal for four different clubs (Juventus, Sevilla, Spurs and Napoli) - the joint-most sides of all Spaniards alongside Fernando Morientes.
'It should hurt' - what they said
Liverpool boss Jurgen Klopp, speaking to BT Sport: "It should hurt because there were opportunities for us. It was an open game with a lot of counter-attacks, but we didn't finish them off and that is a problem.
"In the second half it was a wild game; they were running and we were running.
"I don't think it's a penalty. What can I say? For me, it is clear and obvious no penalty. He jumps before any contact - we can't change that.
"We played a lot of good football but didn't finish it off. We controlled moments but had not enough chances in the end. We made decisions that were not right and have to accept the result. It was very often the final ball that was not right."
Napoli manager Carlo Ancelotti: "The strategy was to play a complete game. High pressure if possible, but also defending deeper if needed. We did everything well. We have to get used to the different moments of the game.
"When Liverpool were in control we did well in defending and then took our chances. It was a very balanced game. So we did well, because I consider them the best team in Europe."
Liverpool travel to Chelsea in the Premier League on Sunday, 22 September (16:30 BST) and do not play in the Champions League again until Wednesday, 2 October (20:00 BST) when they host RB Salzburg at Anfield.
- 22Di Lorenzo
- 6Mário Rui
- 5AllanSubstituted forElmasat 75'minutes
- 24InsigneSubstituted forZielinskiat 66'minutes
- 11LozanoSubstituted forLlorenteat 69'minutesBooked at 90mins
- 4van Dijk
- 26RobertsonBooked at 57mins
- 14HendersonSubstituted forShaqiriat 87'minutes
- 7MilnerBooked at 61minsSubstituted forWijnaldumat 66'minutes
- Dr. Felix Brych
- Shots on Target
Second Half ends, Napoli 2, Liverpool 0.
Goal! Napoli 2, Liverpool 0. Fernando Llorente (Napoli) right footed shot from the centre of the box to the bottom left corner.
Fernando Llorente (Napoli) is shown the yellow card for a bad foul.
Georginio Wijnaldum (Liverpool) wins a free kick in the defensive half.
Foul by Fernando Llorente (Napoli).
Substitution, Liverpool. Xherdan Shaqiri replaces Jordan Henderson.
Attempt missed. Fabinho (Liverpool) header from the centre of the box misses to the left. Assisted by Jordan Henderson with a cross following a corner.
Corner, Liverpool. Conceded by Kostas Manolas.
Corner, Liverpool. Conceded by Giovanni Di Lorenzo.
Goal! Napoli 1, Liverpool 0. Dries Mertens (Napoli) converts the penalty with a right footed shot to the bottom left corner.
Penalty conceded by Andrew Robertson (Liverpool) after a foul in the penalty area.
Penalty Napoli. José Callejón draws a foul in the penalty area.
Foul by Fernando Llorente (Napoli).
Virgil van Dijk (Liverpool) wins a free kick in the defensive half.
Substitution, Napoli. Eljif Elmas replaces Allan.
Attempt saved. Sadio Mané (Liverpool) right footed shot from the centre of the box is saved in the centre of the goal. Assisted by Roberto Firmino.
Substitution, Napoli. Fernando Llorente replaces Hirving Lozano.
Substitution, Napoli. Piotr Zielinski replaces Lorenzo Insigne.
Substitution, Liverpool. Georginio Wijnaldum replaces James Milner.