Just 102 days on from losing the final to Real Madrid on a chaotic night at the Stade de France, the Reds returned to continental action looking for a club-record seventh consecutive European away win.
But Liverpool’s stuttering Premier League form continued into Wednesday’s Champions League opener and they were fortunate to only be three down against Luciano Spalletti’s exciting, new-look Napoli at half-time.
Victor Osimhen struck the woodwork seconds into a game that was only five minutes old when Piotr Zielinski converted a penalty awarded for James Milner’s handball.
Napoli soon had another spot-kick but Alisson Becker denied Osimhen, before Virgil van Dijk – who had given away that penalty – got back to thwart Khvicha Kvaratskhelia with a fine goal-line clearance.
But Liverpool wilted rather than rallied at the cavernous, creaking Stadio Diego Armando Maradona, where ex-Fulham midfielder Andre-Frank Zambo Anguissa and substitute Giovanni Simeone struck before half-time.
Napoli were celebrating a fourth moments into the second half as Zielinski grabbed a smart second, meaning Luis Diaz’s quick response was only ever going to be a consolation.
The celebrations are sure to continue long into the night in southern Italy, while Liverpool will hope their poor start to the campaign has bottomed out with this embarrassing defeat.
Fan safety in Naples had dominated the build-up to the Group A clash and the hardy Liverpool fans that made the trip walked into an extraordinary atmosphere that only improved as a wild first half unfolded.
Only 41 seconds were on the clock when Osimhen raced behind and rounded Alisson to hit the post from an acute angle. It was a warning shot that the Reds failed to heed.
Napoli took the lead in the fifth minute after captain Milner handled in the box, leading referee Carlos Del Cerro Grande to point to the spot. Zielinski kept his cool, sending Alisson the wrong way.
The Spanish official would point to the spot again after VAR Alejandro Hernandez advised him to watch Van Dijk’s challenge when Osimhen attempted to cut inside.
Napoli’s star man stepped up for the 18th-minute spot-kick and struck the same way as Zielinski, but this time Alisson read it to make the save and skipper Giovanni Di Lorenzo blazed over the rebound.
Trent Alexander-Arnold saw an effort saved and Mohamed Salah wasted a fine opportunity as Liverpool briefly improved, before Van Dijk was forced into a fantastic clearance after Osimhen crossed for Kvaratskhelia.
Joe Gomez was all too easily stripped of the ball for that chance and was at fault again when robbed of possession by Kvaratskhelia – a summer signing who has quickly been nicknamed ‘Kvaradona’.
The Georgia international kept the ball impressively before laying back to Zambo Anguissa, who played a one-two with Zielinski and smartly slotted past Alisson in the 31st minute.
The home fans could not believe their eyes and, after Van Dijk and Harvey Elliott threatened at the other end, were celebrating a third as injured Osimhen’s replacement found the net.
Kvaratskhelia beautifully flicked around Alexander-Arnold and then outmuscled Gomez, before hitting a low cross for Simeone to easily turn home.
Joel Matip had an effort saved after replacing Gomez at half-time but Liverpool would concede a fourth just 80 seconds into the second half.
Alisson got down brilliantly to stop Zielinski’s initial first-time strike, but the Napoli man delightfully dinked home as a wild night continued.
Liverpool temporarily quietened the home crowd when Diaz cut in and bent home a low right-footed shot in the 49th minute – a fine strike they attempted to build on.
Diaz saw a thumping header saved by Alex Meret and Darwin Nunez – part of a second-half triple change – saw a shot blocked as the tempo slowed and Napoli began to tire.
The swathe of changes made by both sides – including a Liverpool debut for Arthur – took the sting out of a match that was only heading one way. Both teams had opportunities but the match was long since settled.