"Be careful, Real Madrid," warned Pep Guardiola in the moments after his greatest triumph as Manchester City manager. This was Guardiola in jest rather than setting his sights on the rival club that has defined his career to a greater degree than any other, but in the Spanish capital, they would have taken note.

Guardiola had joked that City were just 13 European Cup triumphs behind Real after they beat Inter in Istanbul last season to break their duck in Europe's premier club tournament. "Kings of the competition," Guardiola called Real ahead of their latest meeting and while on the weight of history that will remain indisputably true, right now they are in danger of being temporarily dethroned.

For the third successive season, these two clubs are meeting deep in the Champions League's knockout stage. In 2021/22 Real Madrid produced the kind of heroic rescue act they made a name from and won a titanic semi-final duel before winning the tournament. A year later, City exacted brutal revenge at the same stage and won the tournament.

The winners of this year's quarter-final will be favourites to go all the way come Thursday morning and it would be no surprise if they did just that. It feels like the balance of power is shifting and if City once again prevail in an Etihad second leg, it will confirm that thought.

It will be their 12th meeting in total since City's ascension to Champions League regulars and it is a rivalry that has simmered away until the stage it is at now, which is the biggest and best in Europe. It is two star-studded teams managed by two of the most successful coaches the game has seen, but who work as opposites in so many ways.

City's first meeting with Real was a 3-2 defeat in the Bernabeu in September 2012, a group stage game that saw Real score twice in the closing stages to turn the game on its head. It was a feeling City would become accustomed to. Even the semi-final under Manuel Pellegrini in 2015/16 felt like a false dawn, given City's failure to land a blow across the two legs.

But now they are the undoubted heavyweights of European football. Barcelona are in financial meltdown and barely able to sustain a challenge to Real in La Liga. In England, Manchester United's tailspin into mediocrity has left the coast clear for City to dominate, despite Liverpool's renaissance and the threat of just that from Arsenal.

The challenge from Paris has never materialised, Juventus are in a constant state of crisis and even Bayern Munich seem to be going backwards, finally toppled in Germany. It is Bayern who could yet lie in wait for City or Real in the semi-finals, but they are unlikely to stop either.

Bayern are the team that Real used to measure themselves against. They both considered themselves European aristocrats and it created a potent European rivalry. But as Iker Casillas suggested last week, in Madrid, it feels like City have taken over Bayern's mantle.

In many ways, they each have what the other wants. City are trying to emulate Real's history and tradition and to build a worldwide brand to match. Real would love the financial muscle City now have and the quality of football they can produce. It's an intoxicating mix on which to contest such defining continental duels.

This week's second leg, finely poised at 3-3 after last week's fireworks, looks to be more evenly matched than a year ago when City kept the hosts at arm's length in the Bernabeu and then tore them apart back in Manchester. Real feel like a better team now and in Jude Bellingham, they have another bona fide star.

And perhaps Real sense their time is coming again. The age profile of their squad is certainly younger than City's, with Vinicius Jr, Eduardo Camavinga, Fede Valverde, Aurelien Tchouameni and Rodrygo all younger than 25. Brazilian sensation Endrick is coming to join them, as almost certainly is Kylian Mbappe.

That will take this rivalry to another level next season, if Europe's two best teams also contain the two most exciting attackers of their generation. City vs Real and Erling Haaland vs Mbappe will be quite the heavyweight billing. It would be deserving of a main event and after two semi-finals and a quarter-final in the last three seasons, maybe it could deliver just that in Munich on May 31, 2025.

If they do meet again next season then there could be another ever-developing sideshow. Real have been so focused on chasing Mbappe that there has been little room for anyone else in that attack in recent years, which is why they have Stoke City flop Joselu as their sole striker this season. But it feels like a matter of time until they try and lay the groundwork for bringing Haaland to the Bernabeu. It's exactly the kind of deal that Perez prides himself on.

In City, he may have met his match. The Blues haven't had to sell an A-lister at any point in Guardiola's reign and they were happy enough to let Brahim Diaz and Emmanuel Adebayor (on loan) move to Real. When it comes to this rivalry, the kings of Europe don't always get what they desire.