There might be a lot of doubt about what the Champions League group stage means in the grand scheme of a season, but there can be no doubting what it means to Liverpool and Paris Saint-Germain - and it makes this a hugely appealing and appropriate curtain-raiser for the new campaign.

That meaning is one common element between clubs with an awful lot of contrasts; contrasts that only add to how compelling this game is.

For both, this is about much more than the relatively mundane aim of getting off to a good start, stating a claim to win the group, and all the rest of that.

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Liverpool want to live up to last season, to show they are still escalating as such an exciting side, and that a club with such a Champions League history can compete amid the economic realities of the modern game.

That is an economic reality, of course, that has effectively been set by PSG. Their record purchase of Neymar remains the landmark move that has had the greatest and most influential effect on the transfer market, and the club game.

Its influence has not yet stretched as far as the Champions League, however, as they still couldn’t get past the round of 16 last season.

The French champions want to live up to that Real Madrid-Barcelona level they so aspire to, to show that theirs is more than just an ostentatious but ultimately empty project, that there is substance to it; the substance of that grandiose silver trophy.

Jurgen Klopp was not impressed by Gary Neville's comments (Getty)

It is also that issue of substance, of a team having heft and authority, that suggests another contrast between these sides - not least the managers, who offer similar parallels.

Jurgen Klopp has so clearly made Liverpool more than the sum of their parts, gradually and forensically improving the team through highly-specific signings for a defined style of play.

To say that hasn’t been the case at PSG would be an understatement. There has been a vague sense of ‘project’, but mostly only defined by amassing an expensive group of players. It’s only a year since Patrick Kluivert was director of football, and that was when the club was already well into this spell of appointing very different manager profiles.

It didn’t help such perceptions that they can seemingly win the French league in second gear, with Neymar not even having to show he is a first-rate talent.

Klopp pointed to how, unlike Liverpool or pretty much any Premier League top-six side, PSG could rest the Brazilian and Mbappe for a league game and still win 4-0, as they did against Saint-Etienne on Friday.

“We watched the game last night," the Liverpool manager said. "They were good, but it was not too important because two of the main men were not involved. But we will analyse them, we started already a bit, so we try to be ready, but they are really good, so that's interesting. I don't see the pressure or whatever for us. People say we were last year in the final so this year we have to win it, come on. So we play against PSG, that's a very interesting football project.”

And this also an interesting dilemma. Figures around PSG admittedly do insist all this is starting to change, and there is now much more intelligent direction, as signalled by the appointment of Thomas Tuchel. The idea is he can give them a focus and attacking tactical idea that has been lacking.

(Getty (Getty)

This, however, might just pose another problem.

Given the indulgent culture at PSG that so many reports have detailed, and particularly that around their Brazilian superstar, the thought of Tuchel attempting to point out specific counter-pressing positions to Neymar is almost comedic.

And there should be no doubt that is precisely what the German will do. As one figure who knows him well attests, and so many in the game say he’s famous for, “he won’t treat the first guy on the team sheet any differently to number 25 in the squad”.

That treatment usually involves “super intensity”, not dissimilar to Klopp, but without his Borussia Dortmund predecessor’s interpersonal touch and much greater nuance.

This is why things ultimately went badly for Tuchel at Mainz, and at Dortmund.

It is far too early to talk about that with PSG, but almost the main point of interest about their season is how they will cope with that intensity, in a situation when they won’t actually need it until February and the Champions League latter stages.

Except maybe Tuchel’s intensity is just what they need? Maybe it is what can finally propel them, and prevent them getting caught cold when fixtures actually develop white heat?

That is why this match against Liverpool is a good one to open the Champions League. The electricity around Anfield on a European night will be a jolt, and one of those they’re going to need at intervals over this season.

There is then the way will Liverpool will put it up to them, testing Tuchel’s structure. And what of Mbappe’s pace against that defence?

Klopp pointed to how different their defending has been, especially against Tottenham, so an attack like that will just be another test; a greater test.

It will start to provide an idea of how far they’ve come on from last season, and maybe how far both sides can go.