Yunus Musah had only heard about it. The fire. The intensity. The bags of urine flying from the stands like gross, golden grenades. Tall tales, you know? Lore. Musah had heard stories, but it wasn't until this summer that he finally saw a sliver of it with his own eyes.

It wasn't his fault he was unaware, either. Musah grew up in Italy, spending his youth soccer days playing in England. He is every bit as American as any other player on the U.S. men's national team -- he was born in New York -- but until June, when he was part of the U.S. roster for the Nations Cup final, he'd never really grasped the singular truth that his teammates with U.S. roots seemed to understand from their first kick of a ball...

... The games against Mexico are different.

"I only realized it then," Musah told me one day last month, his eyes getting wide as he talked about the national anthems, the fireworks and the way the fans shouted and chanted at each other with that incredible heat that felt more like a rolling boil. He laughed. "That's when I realized 'OK -- this is mad.'"

- ESPN+ guide: LaLiga, Bundesliga, MLS, FA Cup, more (U.S.)
- Stream ESPN FC Daily on ESPN+ (U.S. only)
- Don't have ESPN? Get instant access

It is, and it has been this way for decades, with every generation of American players, coaches and fans bringing their own backstory to the rivalry, only to inevitably end up in the same place. There is no debate on this particular subject, and no other perspective. When the schedule for the World Cup qualifying matches was announced, which match did you look for first? Which date did you put in your calendar right away?

Now, finally, it's here again. Friday in Cincinnati. U.S. vs. Mexico (watch on ESPN2 or stream LIVE on ESPN, starting at 9 p.m. ET). Another one of these games that ripples up from the page. That crackles. That feels like the beginning to a new chapter in this story that we all crave the most.

Only this time, it also feels like something is ending.

It should be noted that Musah wasn't being hyperbolic. The atmosphere in Denver for that Nations League final really was something remarkable. The game, which featured the top players from each side, had all the U.S./Mexico hallmarks: contentious refereeing decisions, scuffles, grittiness, absurd emotional swings and, when it was over and the U.S. had won, the haughty dismissiveness from Mexico that comes from a group continuing to hold a marked advantage in the all-time, head-to-head record.

As good as the feeling was that night, though, it was still the Nations League. It was still a tournament without history.

The World Cup qualifiers between the teams, on the other hand, have always existed on a different plane. Theirs is a heightened sense of urgency, of importance, of meaning.

The stakes are incomparable: for teams in North America, the World Cup is alone at the pinnacle. For all its charm, the Gold Cup isn't the Euros or the Copa America; it just isn't. It doesn't have anything close to the same meaning to players or fans that the continental tournaments do elsewhere. Because of that, when Mexico and the United States play in a World Cup qualifier, the match isn't simply about asserting superiority; it's about standing in front of your rival on the road toward the only thing that truly matters.

We know the moments. The "Dos a Ceros." The brutal reverse by Mexico in Columbus five years ago that was part of the American death spiral. The scoreless draws in Azteca in 1997 and 2013. The U.S. has still never won a qualifier there.

Those games are the root drama of this rivalry, its lifeblood. But in terms of carrying meaning, they might be nearly complete. The game at Azteca in this qualifying cycle isn't until March, when one (or both) of the teams could be qualified. And with the 2026 World Cup being hosted by the U.S., Mexico and Canada, those countries won't need to participate in the qualifying tournament at all over the next four years. There will be only friendlies.

Beyond that, FIFA has voted to expand the World Cup field to 48 teams (for now), which means that CONCACAF will receive at least six places in every tournament -- a reality that'll further drain the drama from the already top-heavy confederation. Traditionally, the final round of qualifying featured six teams (the Hex, as it was known) and three were guaranteed spots, giving the rivalry games their edge.

Going forward? With the disparity in resources among the CONCACAF nations, it seems virtually impossible to imagine a situation in which either of the top countries is at risk of missing a World Cup when there are a half-dozen spots available. After all, since 1990, only seven of the 41 CONCACAF nations have even qualified for a World Cup, highlighting just how divided the region really is.

Now, let's be clear: Nobody's saying that the intensity in games between the U.S. and Mexico is going to suddenly disappear. It can't. The players will always bring their own histories to the matchups, and more and more, those histories are infused with passion for the rivalry from the youngest of ages.

When Paul Arriola was 14, he attended a U.S. youth national team camp that involved a trip to that summer's Gold Cup final at the Meadowlands in New Jersey. It was the U.S. against Mexico, and Mexico routed the Americans 5-0. Arriola, who grew up in Chula Vista, California -- right near the border with Mexico -- looks back at that game as a particularly formative afternoon in his career.

"We were all there with our U.S. polo shirts on," Arriola told me. "And every time Mexico scored, we would get beer thrown on us [by the Mexico fans]. I remember getting so angry, and so frustrated that we were kids and these people were showing such passion that they were willing to throw beer on kids." He shook his head.

"Obviously, I have great respect for the rivalry and for the teams and you know, for Mexico and their fans, but it still drives me today to always want to win against them. Because, you know, I carry that extra edge. And that experience that I experienced."

Ricardo Pepi, who will likely lead the attack for the U.S. on Friday, grew up near the border in El Paso, Texas, and makes no secret of where his family's loyalties were when he was younger.

"I'm being honest with you: I always used to root for Mexico just because, you know, my parents rooted for Mexico," he said. "They're Mexican, I grew up watching Mexican soccer, I grew up watching the Mexican national team. And you know, those were times where, you know, we're rooting for the Mexican national team in general. In my household, it's all Mexican culture. And then I stepped foot out of my house and it's all American culture."

He shrugged. Whatever is at stake, a U.S.-Mexico game will always be special for his family.

"I started representing the U.S. and U.S. national teams, and I started feeling something for the crest," he said, "and I said I was going to represent the U.S. with all my heart."

Friday's game feels like the typical powder keg. The U.S. has a young, largely unproven team and has shown the expected inconsistency one would expect from such a group: disappointments like the home draw with Canada or the sluggish performance in the loss against Panama, juxtaposed against the vibrancy of the second half in Honduras or the fightback from an early hole to take all three points against Costa Rica. The unpredictability, for both good and bad reasons, has been persistent.

Mexico, too, hasn't been as automatic as it would like. It took a last-minute goal to beat Jamaica (largely seen as the weakest of the teams in the group) and draws against Panama and Canada (startlingly, at the Azteca) have laid bare their own vulnerabilities. The importance of this game, for both teams, is real.

Does it seem most likely they both make Qatar? Certainly. But there's enough scar tissue from 2018 for American fans, still enough doubt and still enough games left to play in this cycle that the significance of the match has surged. Brenden Aaronson, who figures to be one of many Americans playing in his first qualifier against Mexico, said he thinks it will be "a war." Tim Weah, who came on as a substitute in that Nations League final, told me that was his "first time getting a taste of it. And it was an amazing feeling and I can't wait to get more of it."

He isn't alone; this is what everyone craves. The U.S. and Mexico. A packed stadium in Ohio. A World Cup spot in the offing for those players who can assert themselves.

It is the best kind of night in American soccer, the sort of night that players and coaches and fans see anytime they close their eyes.

Embrace it. Adore it. Revel in it. It might not be quite like this ever again.