A penalty from Dries Mertens and a late poaching effort from Fernando Llorente due to Virgil van Dijk's mistake secured a 2-0 win against the defending champion in the Group E opener.
Liverpool's Champions League title defense started with defeat, as the Reds fell to Napoli 2-0 in Naples to kick off play in the group stage.
An entertaining game at the San Paolo Stadium ended with a victory for the hosts, as a penalty from Dries Mertens and a late poaching effort from Fernando Llorente secured the win in their Group E opener. It marked the second straight season Napoli won at home against Liverpool following a 1-0 triumph in the group stage last season.
It was an enjoyable game for the neutrals, one in which two attack-minded, pressing sides went at each other. Carlo Ancelotti's side just about had enough to secure a big win against Jurgen Klopp's squad, though, and earned a valuable three points.
As expected, the game started at a fast pace, as Napoli looked to enforce its will in the final third with its offensive weapons. Liverpool, being one of the best counterattacking teams in the world, quickly looked to capitalize on the break using Mohamed Salah as its target man.
Meanwhile, on the other side, Napoli's Lorenzo Insigne, who scored the winner at home last season, caused headeaches on the left. The home side's first real attempt, though, came from Mexico's Hirving Lozano, who headed the ball in the net from close range after Adrian had stopped an initial long-range effort, but the linesman ruled it off for a clear offside.
In the 20th minute, Sadio Mane got involved in the action with a shot from inside the box, but Napoli goalkeeper Alex Meret was up to the task and blocked the Senegalese attacker's attempt. Insigne kept pulling the strings as his ball found Mertens in the 24th minute, and the Belgian star crossed in a delightful ball from the right wing, but Liverpool's back line stood firm and cleared. Just before the halftime break, Roberto Firmino had a great opportunity to make it 1-0 with a solid header from a corner, but it went wide.
The second half began just like the first as Napoli came extremely close. Mertens picked up a great cross from Mario Rui and attempted an audacious volley from close range but Adrian was up for the task and just about did enough to deny the Napoli forward, making an acrobatic, highlight-reel save to keep the match scoreless.
In the 64th minute, Salah got another chance, as Manolas poorly timed a clearance and the Liverpool attacker took full advantage by entering the box and shooting from inside the box, but Meret pushed the low attempt wide from his goal.
Mane had another shot in the 73rd minute but, again, Meret collected with ease.
As Napoli pushed for the go-ahead goal, Jose Callejon penetrated the box and Andrew Robertson seemed to have just clipped him. The ref agreed and gave a penalty, though replays showed that Robertson played the ball and Callejon fell over him. Nevertheless, Mertens took it and made it 1-0 from the penalty spot.
It seemed it would stay 1-0, but an uncharateristic mistake from the usually reliable Virgil van Dijk allowed Napoli to press and Llorente added the second goal to put the result away.
Here were the lineups for both sides:
Liverpool and Napoli are the favorites in Group E and will play RB Salzburg and Genk in their next pair of group matches. Salzburg tops the group on goal difference after one set of matches following a 6-2 win over its Belgian opponent.