Liverpool have it all to do if they are to keep their Champions League hopes alive.
The Reds fell to a 2-1 defeat to Paris Saint-Germain at the Parc des Princes, meaning they must beat Napoli on the final matchday by two clear goals if they are to have any chance of progressing to the last 16.
In the French capital, it proved another disappointing away European game for Jürgen Klopp's Reds. This latest reverse means that they took zero points on the road in the Champions League this season having also failed to score from open play.
Goals from Juan Bernat and Neymar condemned Liverpool to a fourth consecutive away defeat in European competition for the first time in the club's history.
James Milner scored a penalty late in the first half but it was not enough as Thomas Tuchel's side held on for a crucial win.
Front three not firing on all cylinders
There can be no doubting the contribution of Liverpool's much-vaunted front three. Since the start of last season, Mohamed Salah, Sadio Mané and Roberto Firmino have scored 35 of the Reds' 48 Champions League goals. That's a rather staggering 73 per cent.
However, while Mané won the penalty which ultimately gave Liverpool hope, they were far from their best. It was a shame. With Thilo Kehrer at right-back and a risk-taking Presnel Kimpembe beside Thiago Silva in the centre of Les Parisiens‘ defence, the home side were far from insuperable at the back.
Indeed, after Milner tucked away the penalty to halve the deficit, the reaction from the PSG players was far from convincing and Klopp will be disappointed that his most-advanced trio were unable to strike up the understanding that has established them as one of the most devastating front lines in European football, particularly against a defence which looked capable of conceding chances under pressure.
By the time Roberto was replaced by Daniel Sturridge with 20 minutes remaining, the Brazilian had lost more duels than any other player on the pitch and had managed just 38 touches overall, failing to create a single chance.
PSG have not impressed when it's come to major Champions League games away from home. Last season, they fell to a 3-1 defeat to Real Madrid in the last 16 and, of course, two seasons ago, they capitulated at the Camp Nou to lose 6-1 to Barcelona and somehow squander a 4-0 advantage from the first leg.
However, while they have work to do in asserting their authority on the road, the Parc des Princes remains an impenetrable fortress. They're now unbeaten in 21 Champions League group games at home (their last defeat coming against CSKA Moscow in December 2004) and have recorded some emphatic victories along the way, including a 6-1 demolition of Red Star Belgrade in October.
This was less emphatic but there can be no question that PSG at home looked a completely different beast to the disjointed – and at times disinterested – outfit that were outclassed and outthought at Anfield in September.
Home form alone won't get them far but, as Liverpool discovered tonight, the Parc des Princes is as intimidating as it gets for a visiting side. Slick and inventive and with a front three to die for, it was a tough night for the visitors' defence.
Tactical flexibility causes problems for Reds
PSG, at times, were overwhelmed in that game at Anfield but it was the opposite here; Thomas Tuchel's flexible set-up, switching between a back three and four, made the runaway Ligue 1 leaders look sharp, dynamic and highly dangerous any time they poured forward.
They didn't seem to miss Adrien Rabiot in midfield. Marquinhos, an energetic but disciplined presence in front of the back four, allowed the more adventurous Marco Verratti to roam forward.
Liverpool's midfield three of James Milner, Jordan Henderson and Georginio Wijnaldum struggled with the tempo and intensity, particularly in the first half, when Neymar and Kylian Mbappé charged through the centre on several occasions.
Klopp's midfield three was ineffective, as it was away to Napoli and Red Star Belgrade. They were unable to control the game and it meant PSG largely dictated the tempo.
But even when Livrpool did threaten, they struggled to get past an immensely pumped-up Thiago Silva, who wildly celebrated his tackles and blocks as though they were goals in a gloriously unapologetic display of proper defending.
Marquinhos, too, enjoyed an excellent game.
Fast-tracking VAR a must for CL
Reports emerged last week that UEFA are accelerating their introduction of VAR so it can be used in the knockout rounds of the Champions League.
If we take the performance of Polish referee Szymon Marciniak here as a measure of how badly officials need assistance, it can't come quick enough.
Marciniak failed to send Verratti off following the Italian's reckless challenge on Gomez and, had it not been for the fifth official, Liverpool would not have been awarded the penalty on the stroke of half time despite Angel Di María's desperate lunge on Sadio Mané.
The impact Verratti's dismissal would have had on the complexion of the game is obvious and it was certainly a decision that would have been reviewed. Liverpool will rightly feel aggrieved that the midfielder got away with just a yellow.
Marco Verratti gets booked for a late challenge on Joe Gomez…
Should it have been red?! pic.twitter.com/XamnwetWhr
— Football on BT Sport (@btsportfootball) November 28, 2018
Gomez struggles not what Klopp needed
We wrote earlier this week that Trent Alexander-Arnold was set to face a real acid test in Paris after a couple of shaky performances away in Europe this season.
In fact, Klopp felt more secure in omitting the 20-year-old from the starting line-up, recalling Joe Gomez to the right-back slot with Dejan Lovren partnering Virgil van Dijk at the heart of the back four.
It initially seemed a shrewd move from the German. Although Alexander-Arnold scored a beautiful free-kick in last weekend's win at Watford, the feeling is that he is still a little early in his development for these pressure-packed assignments on the road in Europe.
However, Gomez's struggles were not what Klopp had ordered. He was out of position in the build-up to PSG's opener and, having recovered, he was sluggish in his attempts to stop Bernat. For the second, Gomez – again high up the pitch – should have taken Neymar out as the Brazilian flew past him and slotted in Mbappé down the left flank.
Don't be surprised if Gomez returns to centre-back for the visit of Napoli with Alexander-Arnold restored to right-back.