Carlo Ancelotti has been around long enough to know these are the games that really matter at Real Madrid.

A Champions League last-16 tie against Paris Saint-Germain, with all the noise, the drama and the intrigue, will carry greater significance for Madrid’s president Florentino Perez than any of their other 39 fixtures so far this term.

In 2018, Zinedine Zidane launched his entire coaching career off winning titanic battles like these.

No matter that Real Madrid finished almost 20 points behind Barcelona in LaLiga. Zidane marched his team past four European heavyweights in the knockout stages – PSG, Juventus, Bayern Munich and, in the final, Liverpool – and was instantly hailed a genius.

If success in Europe can excuse domestic failure at Real Madrid, the reverse is also true.

Winning LaLiga this season, however, may not be enough to prevent serious questions being asked about the direction of the club if it is PSG celebrating at the Santiago Bernabeu.

Ancelotti knows the demands better than anyone. He experienced them in 2015, after leading Madrid to the yearned-for ‘La Decima’ – the club’s 10th Champions League crown – only to be sacked the following season.

“Madrid is not a club where you put down roots,” he wrote in his book ‘Quiet Leadership’ in 2017. “You are only ever a piece of the project.”

Even when Real Madrid appointed Ancelotti last summer, it felt more like a marriage of convenience, Perez finding a trusted guardian to smoothen out a period of transition after Zidane’s departure and the financial uncertainty caused by the pandemic.

Ancelotti, meanwhile, grabbed an unexpected chance to manage at the very highest level again.

It has worked out better than perhaps either imagined. Real Madrid’s 4-1 win over Real Sociedad this past Saturday sent them eight points clear at the top of LaLiga, which they will surely now win from here.

A commanding performance certainly suggested they can overturn their 1-0 deficit against PSG.

But for as long as Madrid continue to rely on a core of players in their thirties and coaches who manage rather than build, familiar questions remain: How long can it last? And then, what comes next?

Two figures at PSG throw those questions into even sharper focus.

Kylian Mbappe’s scintillating late winner in the first leg in Paris appeared to be both deflating and thrilling for Madrid supporters in equal measure.

Many felt they were getting an up-close preview of a player that will be theirs in the summer.

Such is Mbappe’s quality and appeal, his arrival at Real Madrid would grant the club a generational shift in one move, a 23-year-old superstar to instantly build a team around.

Mbappe would update their style and restore their status, Real Madrid once again with a side not just to be respected, but feared.

The other pertinent figure is PSG’s coach Mauricio Pochettino, whom Madrid have coveted for the last five years and strongly considered to replace Zidane in 2018.

“I take it as something positive that Madrid think highly of me,” Pochettino said the following year.

Pochettino’s time might at Madrid yet come but he is also symptomatic of the kind of modern, intense, hands-on coach they have steered clear of, in favour of more conservative appointments like Zidane, Julen Lopetegui and Ancelotti.

Others have been bolder. PSG have gone for Pochettino, Bayern Munich for Julian Nagelsmann, Chelsea for Thomas Tuchel and Barcelona for Xavi Hernandez.

Manchester City and Liverpool are still the teams to beat with Pep Guardiola and Jurgen Klopp. Juventus have reverted to Max Allegri –but not before they tried Andre Pirlo.

Ancelotti has looked a good fit to prolong the likes of Luka Modric, Karim Benzema, Toni Kroos and Casemiro, who have been key to Madrid’s dominance in LaLiga. Modric and Benzema, in particular, have been outstanding.

And there is no doubt Madrid’s veterans can find a different gear when the Champions League music plays. Few would be surprised to see them find a way to prevail on Wednesday.

But these matches serve as a litmus test, too. With Barcelona and Atletico Madrid struggling, these games are a truer indication of where Madrid are now in comparison to the elite.

After defeating Liverpool last season, Madrid were outplayed by Chelsea. The year before, they were convincingly beaten by City.

This is the challenge this week for Real Madrid against PSG; for Ancelotti and his players to prove they are still relevant, not just in Spain, but at the highest level, a force for the present rather than relics of the past.