As far as Clasicos go, the final 2017-18 iteration of global soccer’s most famous rivalry will be relatively inconsequential. That is, it won’t change the shape of La Liga. With four games remaining, the title is already Barcelona’s. Real Madrid’s season has been one of domestic disappointment, but Champions League qualification is secure. Sunday’s showdown (2:45 p.m. ET, BeIN Sports), which eight months ago figured to be decisive, is anything but. A quick glance at the league table, in fact, would tell you it’s meaningless.

But a quick scan of Barcelona’s league results, and a rudimentary knowledge of a rivalry that transcends sport, would suggest otherwise.

That’s because Barcelona is four games from invincibility. Four away from the first 38-game unbeaten season in Spanish top-flight history. Four games from immortality. And Madrid is the last towering obstacle standing in its way.

Barca is four games away from something that has never been done before, which, in a rivalry littered with so much success, is a rare opportunity. The battle for Spanish superiority has, from a historical perspective, become one of sheer quantity. Ask any fan – especially a Madrileño – which club has had the upper hand, and they’d likely point to Real’s 95 head-to-head victories compared to Barca’s 92; to Real’s 33 league titles compared to Barca’s 25; to Barca’s 30 Copa Del Rey crowns compared to Real’s 19; to Real’s 12 European titles compared to Barca’s five.

There is far more to the rivalry than trophy counts, of course, but trophies are emblems of on-field success. When both teams have won everything there is to win, success is measured not by degree but by frequency. Barcelona’s 2017-18 title, if it were just any old title, would wane in importance over time. It would become a tally mark, one small part of an increasingly large number.

But even the on-field aspect of the rivalry is not exclusively defined by numbers. The numbers are accentuated by the players, teams, eras and legacies that give them life; the ones that stand above the rest. Barcelona will never have an Alfredo Di Stefano, nor Real’s still unequaled five consecutive European Cups. Real Madrid will never have a Johan Cruyff and the ethos he instilled at Camp Nou and La Masia. It will never have Xavi, Andres Iniesta and the homegrown generation that was in so many ways a footballing extension of the club’s ideals. It will never have the first Spanish treble.

That’s why invincibility matters. Only one of the two clubs can be the first to achieve it. And Barcelona is closer than anybody has ever been before. Just like a playing style or a club identity, an unbeaten season would be a distinguishing characteristic, and a unique expression of primacy – both things that Real Madrid, as a club, is so intent on extinguishing outside the Santiago Bernabeu.

Real’s identity is built on supremacy, but also a suppression of all possible challengers to it – just like the dictatorship of Francisco Franco, to which the club is mythically – though not fictitiously – linked. Real Madrid, to be Real Madrid, not only must be the king; it must be the undisputed king. It has been Spain’s most successful club since Di Stefano and Ferenc Puskas arrived in the capital, and will hold that title for the foreseeable future.

But Barcelona has encroached, and is encroaching. Every unique achievement is a threat to Real’s kingdom, an affront to its preeminence. Barca perfection – or rather Real’s inability to accomplish it first, after being first to so many other milestones in Spanish soccer – would be a sign of Madrid weakness that the club refuses to accept.

In general, there has been a hesitance to accept the greatness of this Barcelona team. There is a thought that, by the club’s high standards, this Blaugrana edition is rather ordinary or underwhelming. Real Madrid, coincidentally, will not give the Catalans a pasillo, or “guard of honor,” as is customary for opponents of already-crowned champions. It will not recognize a mere championship.

But an undefeated season would make Barca’s greatness irrefutable. It would infringe upon Real’s position at the forefront of the record books. And that’s why Sunday, though technically meaningless, is in reality anything but. Los Blancos can’t prevent a parade that has already happened. They can, with a win at Camp Nou, ensure that this Barca team will ultimately be forgotten.

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Henry Bushnell covers global soccer for Yahoo Sports. Have a tip? Question? Comment? Email him at henrydbushnell@gmail.com, or follow him on Twitter @HenryBushnell, and on Facebook.

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