The football handbook isn't exactly clear on when a blip becomes a full-blown crisis. But Liverpool surely veered into that territory at some point during a wretched 90 minutes at Napoli.
Perhaps it was inside five minutes when, after striking the outside of the post just 42 seconds in through Victor Osimhen, Piotr Zielinski scored from the penalty spot following James Milner's handling?
Maybe it arrived when Andre-Frank Anguissa sauntered beyond three players with a basic give-and-go before sliding it past Alisson Becker with just half an hour played?
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Or it could have been the moment Kvicha Kvaratskhelia skipped by Trent Alexander-Arnold in style before outmuscling Joe Gomez for Giovanni Simeone to convert?
If your answer is none of the above, it will have been when Zielinski impudently clipped it over a floored Alisson for 4-0 just moments after the restart.
Wherever your own judgement call lands, there can be little denial now that Liverpool's early season spluttering has evolved into something entirely more serious. This is now the most concerning period since early 2021 when they lost six home games on the bounce behind closed doors and a top-four finish looked like a pipe dream.
This just doesn't happen to Liverpool. They lost only four of 63 games last term and one of those was ultimately meaningless as they eased past Inter on aggregate in the Champions League. That, though, is consigned to the past. In the here and now, the Reds are as ripe for a hiding as they have ever been under their current manager.
The sound of the 'oles' from the home fans in the closing seconds will have been like nails on a chalkboard in front of a megaphone for the visiting contingent but it was nothing less than Napoli deserved.
From front to back, Liverpool look like a hollow husk of the team that sailed so close to footballing immortality just a few months ago. Did that 'failure' to land an unprecedented quadruple cut deeper than anyone is daring to let on? Or is it just the natural drop-off that comes when a near six-month list of fixtures that is laced with peril and meaning across four competitions every single week is suddenly no more?
Whatever the real answer, it's one Jurgen Klopp must quickly get to the bottom of. No lasting damage has been done here in Champions League Group A apart from the morale battering of a 4-1 loss. Their domestic hopes are yet to be extinguished too, despite taking just half of the 18 points available to them.
But if this sobering and at times harrowing defeat is to stand for anything, it has to be the moment Liverpool engaged with reality and started to perform like the team their reputation paints them as.
Klopp resisted what would have been the considerable urge to recall Thiago Alcantara to the starting lineup as a midfield three of Harvey Elliott, Fabinho and Milner was selected. Roberto Firmino was rewarded for his showing off the bench in Saturday's Merseyside derby draw by starting ahead of Darwin Nunez.
After striking the outside of the post almost immediately, the hosts were given a penalty when Milner was judged to have handled a goal-bound shot. Zielinski dispatched his first of the night as Klopp's side fell behind for the fifth time already this season.
Milner's laboured start continued as he clattered into Anguissa moments later to pick up the first booking of the game. The veteran has been a vital part of the success enjoyed these past few years but the 36-year-old now appears like what he is; a player whose professional debut came 20 years ago.
Napoli could even afford the luxury of a missed penalty as Osimhen bizarrely took the duties from Zielinski before seeing his spot-kick saved by Alisson.
Liverpool started the second half as poorly as they did the first as Zielinski reacted first to his saved shot to dink over the goalkeeper and make it 4-0. The Poland international was a one-time transfer target many moons ago and on this evidence, he'd be the outstanding midfield operator now at Anfield. It's the area that is crippling ambitions the most right now after all.
Luis Diaz forced one back with a superb finish after good work from Andy Robertson two minutes after Napoli's fourth and Klopp then sent on Diogo Jota, Darwin Nunez and Thiago as Firmino, Milner and a badly out-of-sorts Salah made way.
That fact that Salah made way at 4-1 spoke volumes about the paucity of his contribution and two first-half moments in particular encapsulated the Egyptian's evening. The first was when a simple pass from Elliott drifted under his foot before he was easily brushed aside while trying to retrieve it. Another was when his touch deserted him with acres of space inside the box to control an excellent pass from Alexander-Arnold at 1-0.
Having finally resolved his future before enjoying the wide range of benefits of a full pre-season schedule, Salah was expected to hit the ground at speed this term. Whatever's eating last season's top scorer remains a mystery but he is as out of form as anyone at present.
The sight of Liverpool probing and passing in an effort to find a goal while they trailed was in-keeping with this campaign, but a quick glance at a scoreboard that showed them trailing by three will have been the real surreal moment for the small contingent of fans who'd made the journey here. Liverpool can lose, sure. But not like this.
Debates can rage about a lack of midfield investment and an unrelenting, unforgiving injury list and there is merit to it all, but the lack of application and attitude from too many in the lineup is now a major problem that must be addressed decisively.
A third visit to this stadium yielded the most disappointing defeat yet for Klopp. How the Reds manager must loathe this little corner of Italy.
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