Liverpool suffered a horrifying shock in Serbia as two goals from Milan Pavkov were enough to give underdogs Red Star Belgrade a stunning victory in their Champions League encounter.
A win for the Reds would have taken them four points clear at the top of Group C. However, the shock result of the competition so far this season means whatever the outcome between Napoli and Paris Saint Germain, Liverpool will be knocked off of the top spot.
Forward PavKov - who was an unused sub at Anfield - headed his side into the ascendancy after 21 minutes before thundering home a powerful effort that left Jürgen Klopp's side completely bewildered.
The hosts dominated the first half proceedings and eventually eased their way to their first three points of the campaign.
There were early warning signs for Liverpool when Vujadin Savic and El Fardou Ben Nabouhane came close before Povkin pounced to give the home side the lead.
The outcome of the match could have been completely different had Daniel Sturridge not squandered a great chance from six-yards out in the 17th minutes that went blazing over the crossbar.
Despite dominating 80% of possession and hitting the woodwork twice in the second half the Reds never really looked like threatening and the result certainly didn't flatter the outstanding home side.
It was a heroic win for the Serbian champions who recorded their 10th clean sheet in their last 15 appearances to make the outcome of Group C almost impossible to predict.
Reds fail to react to early warning signs
The Red and Whites inspiring manager Vladan Milojevic spoke of the importance of home advantage and the crowd repaid their boss' confidence in some fashion with an electrifying atmosphere from start to finish.
After Liverpool walked out to the traditional sea of red and white and the fans' pre-arranged display you could sense it rattled a few players.
An early warning from winger Marko Marin reminded Klopp's outfit that tonight's fixture would not be the stroll in the park displayed at Anfield a fortnight ago when his tackle saw the first booking after only five minutes.
Liverpool began the game as if it were a straightforward affair. The midfield were non-existent in the first-half failing to grab any sort of stronghold on the affair which the visitors to their credit took full advantage on.
Red Star eventually won a corner after Alisson punched away and a Ben Nabouhane effort from range had the visitors trembling from the early threat.
Marin's delivery was met by a thumping header from Pavkov to send the home fans wild.
The hosts' celebrations were exemplified when Pavkov picked up the ball in a deep position before shrugging off a complacent Gini Wijnaldum with ease before advancing at the Reds' back four.
Nobody thought to close the Red Star man down as he had a go from distance before his 25-yard effort flew into the top corner.
Qualification under threat
Liverpool may have turned up for the match but they certainly weren't at the races in Serbia and their lacklustre performance was punished on a truly embarrassing night for the Merseyside club.
An enthralling encounter with Arsenal on the weekend looked to kick the stuffing out of Liverpool this Tuesday evening as Belgrade punished Klopp's deflated outfit.
The midfield trio were completely bullied by the hosts and the visitor's sloppiness with the ball had their German manager so enraged he had nearly the whole substitute bench warming up after only half an hour played.
Klopp has been left with many shortages in midfield, given the injury to Jordan Henderson. Naby Keita was fit enough to make the bench but didn't feature on the night, while Adam Lallana made just his second start in Europe since 2014.
Having originally been favourites to qualify from Group C before kick-off had even arrived, the complexity of the contest completely turn on its head and suddenly Liverpool may face a nervy end to see if they qualify for the knockout stages.