Naples: Dries Mertens and Fernando Llorente scored late as holders Liverpool fell 2-0 at Napoli in the opening match of their Champions League title defence on Tuesday.
Mertens converted a penalty on 82 minutes and Llorente added a second in stoppage time as Napoli gained a measure of revenge for last season's 1-0 defeat at Anfield that denied the Italians a spot in the knockout rounds.
The loss for Jurgen Klopp's side makes them first reigning European champions to lose their opening game of the following campaign since AC Milan in 1994.
However Liverpool, who sit top of the Premier League after five straight wins, remain favourites alongside Napoli to progress from Group E despite Salzburg's thrilling 6-2 win over Genk.
"Give us a few more games to change the table, but it looks like Napoli are through," said Klopp, who tipped the Italians to go far.
"Napoli can win the competition. If you have a good plan and good players, you don't have to be the best team in the world to win the Champions League. You have to perform at the right moment."
Liverpool also lost their group-stage match in Naples last season before going on to lift a sixth European Cup.