The two sides, who shared two entertaining encounters in the competition last season, both had chances as Alex Meret and Adrian made important stops, with the game goalless until Andy Robertson felled Jose Callejon.
Belgium forward Mertens just about slapped the ball past Adrian, who got his fingertips to the strike but couldnt stop it, before Llorente capitalised on a misplaced Virgil van Dijk pass to score, consigning the Reds to their second defeat of the season and their first in 90 minutes.
Key Talking Point
Cast your eyes back to last seasons Champions League. Its Liverpool vs Napoli at Anfield on the final matchday of the group stage. Arkadiusz Milik has the chance to equalise late on following Mohamed Salahs 34th minute strike, thus taking Napoli through to the knockout stages.
Alas, the rest is history. Napoli dropped into the Europa League and were eventually dumped out by Arsenal, while Liverpool would go on to win Europes elite club competition.
Needless to say, a lot more is expected from Napoli this time around. Yes, theyve again been placed in the same group as Liverpool, but neither Salzburg or Genk are exactly Paris Saint-Germain, the club which joined the Reds and I Partenopei in Group C last season, so the Italian side are expected to reach the knockout rounds.
They went toe to toe with the European champions and got their chance to open the scoring when Callejon was brought down.
Mertens, who is closing in on second place Diego Maradona in the clubs goalscoring ranks, made no mistake from the spot before substitute Llorente latched on to a sloppy Van Dijk pass to fire in and get Napolis Champions League campaign off the best possible start.
Starting XI: Meret (8); Lorenzo (7), Manolas (6), Koulibaly (7), Rui (7); Callejon (7), Allan (7), Ruiz (6), Insigne (5); Mertens (7), Lozano (5).
Substitutes: Zielinski (6), Llorente (7), Elmas (5).
STAR PLAYER - Its fair to say that when you play Liverpool, youll need your goalkeeper to make a few good saves.
Meret made a number of important saves, even bailing out Kostas Manolas when the Greek defender gave the ball to Salah in a dangerous position.
He set the platform for Napoli to snatch the win late on, and his name also sounds like the word merit, so well give him the honour here.
Their keeper looks good. Definitely earned his place on Meret.
— Phil Blundell (@PhilBlundell) September 17, 2019
That save was not without Meret.I’m very sorry
— FootballJOE (@FootballJOE) September 17, 2019
Key Talking Point
All eyes were on Liverpool on Tuesday night as the holders began their campaign in Europe.
The Reds secured their sixth European crown in June when they eased past Tottenham 2-0 in Madrid, and most were expecting Jurgen Klopps side to do the same to a good Napoli side.
However, they were made to sweat early on, Adrian pulling off two sharp saves in quick succession as the hosts made a strong start. The former West Ham stopper also pulled out a fabulous stop to deny Dries Mertens, springing to his left to connect with a sprawling hand to tip the ball over the bar.
They were, expectedly, sharp on the counter, but lacked a clinical edge to make the most of their opportunities - Sadio Mane was one such guilty party, shooting straight at Meret when Trent Alexander-Arnold was ready to receive a pass in a more advantageous position.
Starting XI: Adrian (8); Alexander-Arnold (6), Matip (6), Van Dijk (5) , Robertson (5); Henderson (7), Fabinho (7), Milner (6); Salah (5), Firmino (6), Mane (7).
Substitutes: Wijnaldum (5), Shaqiri (5)
STAR PLAYER - Even though Napoli only stole the lead late on, Liverpool would have fallen behind earlier had Adrien not pulled off a stunning save.
Fabinho also put in a reliably assured performance, but Adrian is starting to convince fans that he can fill in capably in Alissons absence.
Wow. Adrian has just made the save of the season
— Matt Le Tissier (@mattletiss7) September 17, 2019
Liverpool will face a stern test of their Premier League title credentials when they face Chelsea at Stamford Bridge on Sunday. Theyre next in action in the Champions League in early October, when they play Salzburg, who smashed Genk 6-2.
Napoli have a trip to newly promoted Lecce on Sunday, with their next European tie being a trip to Belgium to face Genk.