“Le grand Paris reste une idée, un fantasme qui tourne dans nos rêves mais ne se traduit pas vraiment dans les matchs.”

Some things just sound better in French. See for example the above, taken from a report in Le Parisien of Paris Saint-Germain’s 2-0 home win against Nantes in midweek. This is definitely best read in the original, ideally in the sad, sonorous tones of Uncle Monty from the film Withnail and I staring wistfully out of a scullery window with a firm young carrot in one hand and a velveteen club-branded Neymar figurine in the other.

Une idée, un fantasme dans nos rêves. What the man from Le Parisien is saying here, coming on like a cross between Baudelaire and a Fan TV stadium vox pop, is that PSG are in a bit of a state these days, albeit a fascinating one. This is still a winning machine. Victory on Wednesday left Thomas Tuchel’s team five points clear at the top of the table and they are already guaranteed first place in their Champions League group. Mauro Icardi and Edinson Cavani are an unusually regal pair of back-up strikers. In Idrissa Gueye and Marco Verratti they have a passing, covering midfield to die for.

But something is still rotten in the state of Denmark. It is two and a half years since the most extraordinary single recruitment blitz in the history of sport. Neymar came to Paris first, snapped up in early August 2017 for a brain-mangling £198m. Kylian Mbappé followed three weeks later, in a deal rebranded, for obvious reasons, as a temp-to-perm loan. At the end of which Neymar and Mbappé have played just one (yes, one) Champions League knock-out game together in two years. Neymar missed both games against Manchester United with a foot injury last year. Before that both men played in the first leg defeat at Real Madrid, with Neymar once again injured for the decisive defeat in Paris. Fast forward to the present day and the Neymar‑Mbappé mini-era feels like it’s on the brink: caught between heaven and earth, still brilliantly high-functioning, but fragile too, and reaching the end of something.

Mbappé scored the opening goal against Nantes, a clumsily, elegantly inventive little flick of the heel executed while tumbling over backwards. On 78 minutes he wandered off the pitch and sat looking sad and betrayed beneath a red blanket. A little later Neymar also ambled off looking even more broken, devastated, saddened. Neymar had just added the second goal, a penalty celebrated with a shushing gesture towards parts of a crowd that continue to boo him for trying to force a move away, and for not being Cavani.

Neymar (left) is congratulated by Kylian Mbappé after opening the scoring against Nantes at the Parc des Princes on Wednesday. Photograph: Franck Fife/AFP via Getty Images

It was a significant moment in other ways. Get this. Wednesday night was also the first time Neymar and Mbappé had scored in the same game since January, 10 months during which they had spent only 120 minutes on the pitch in each other’s company. It makes for an extraordinary running total: £90m in wages since PSG’s two-man galáctico unit scored in the same game. And beyond that a combined wage and transfer bill of £570m on the pair of them.

Here we have an entire half-a-billion goalscoring project based on getting these two men on the pitch together in the Champions League latter stages. At the end of which Neymar and Mbappé have played only one Champions League knockout games together in two years, the 3-1 first-leg defeat at Real Madrid in 2018. Neymar missed the return defeat in Paris with a foot injury and another ruled him out of both legs of last season’s tie against Manchester United.

This situation would be more obviously comic if Mbappé and Neymar had proven to be a dysfunctional, poorly matched pair. But the truth is more subtle than that. The fact is they are great together. In 46 Neymar‑Mbappé games PSG have scored 150 goals, including 20 mutual assists. To date the real high-summer period was between September last year and January this, when they scored together in 10 games and PSG regularly racked up five or six.

At which point, enter injury, stasis and unrest. It seems possible Mbappé will finally go to Madrid next summer. Neymar has been wandering around looking like a royal prince on a tour of a Victorian sewerage unit for at least the last six months. But both are now fit. From here they have a contained five-month run to make this work, to cut through all the animus, the interests, the industrial-sporting complex that follows these human talent-units around.

Two things are pretty clear. Firstly, when he’s fit Mbappé is the most devastating centre-forward in the world. And secondly while he might be infuriating, an absurd sun king-ish figure, Neymar is also an amazing footballer, with a style that complements Mbappé perfectly when he dials back the showy jinks. How far can they take it now, with one more Champions League season to reach the end of this?

Paris Saint-Germain: the Qatar Years may be a grisly thing in many ways. This is sport as a machine to gloss and launder the status of a wildly ambitious petro-state. You can’t kill the spirit though and PSG are a genuinely engrossing team right now, a group of players with a wonderful purity about them in those moments when football becomes just a thing on a rectangle of green, a business of shapes, angles, talent.

For all the inanity and greed of the European club scene it is worth remembering that sport will still give us these defiant notes of beauty and poise. In this case, and most obviously, an attacking partnership that really does have a touch of heaven about it.

• This story was corrected on 6 December 2019 to reflect the fact that Neymar did not play against Manchester United in the last 16 of the 2018-19 Champions League