John Mueller grew up in Knoxville, going to famed Neyland Stadium to watch University of Tennessee football games alongside 102,000 rabid fans. He has spent the past six seasons attending nearly every Nashville SC match, first at Nissan Park, then for the past two seasons at the rowdy, frequently sold-out Geodis Park, the team's 30,000-seat soccer-specific stadium.

He's been to plenty of loud, boisterous hometown affairs. And yet, Aug. 19, 2023, was something different entirely.

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"Geodis, the night of the Leagues Cup final, is the loudest stadium environment I can remember," Mueller, the secretary for NSC supporter group The Assembly, said.

The evening was loud because of the MLS club attempting to win their first trophy. But there was another reason, a man in the building. Lionel Messi, to be specific. The Argentina international's shock arrival in North America sparked Inter Miami CF on the field -- the last-place club ran through Leagues Cup, defeating Nashville 10-9 on penalties, and won their first MLS match of the second half of the season -- and fans off it.

In Dallas, in Philly, in Cincinnati, in New York, in Los Angeles this weekend, in Publix (!), the Messi Show is loud, boisterous, and celebratory, even when the boobirds arrive.

The Boo's come for Messi pic.twitter.com/T2RknD5Y0p

MLS Moves (@MLSMoves) August 20, 2023

"That wasn't necessarily planned so much as it was every game has a villain," Mueller said. "Sometimes it's a center-back who commits a bad foul or a goalkeeper who starts time wasting in the first half. For that game, it just happened to be him."

In Philadelphia, they called it the Messi Circus.

"The word 'carnival' is thrown around a lot, but it's true," Sons of Ben game day coordinator Robert Migliaccio said of the atmosphere at the Leagues Cup semifinal on Aug. 16. "You had vendors out the wazoo on all the streets selling different things. Yes, they're selling the Messi jerseys, but they're also selling food and drinks, and anybody that could cash in on the Messi effect did."

Local news channels, often slow to cover the Union until they make a deep playoff run, set up live shots outside Subaru Park in Chester, Pennsylvania.

Even with the Union going down early, "the stadium was still electric and loud throughout," Migliaccio said. "My capos and drummers probably had one of the best games of their lives." The Union faithful booed Messi as well, but, you know, Philly fans will boo anyone anytime. It's part of their charm.

At Red Bull Arena, nearly 27,000 fans shouted, "We want Messi," breaking into cheers when he came on in the 60th minute in a match that New York Red Bulls general manager Marc De Grandpre said would be the largest-grossing revenue gate for an MLS fixture in club history. (We'll get to ticket prices in a bit ...)

Making his official MLS regular season debut...Leo Messi.

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Major League Soccer (@MLS) August 27, 2023

It's been a remarkable debut month and a half for Messi & Co: six wins, three draws, plus-16 goal differential, dozens of highlights, one trophy, another final to play in the U.S. Open Cup, scintillating football, far from a retirement league.

"The part of it that's most appreciated from my perspective is that he tries and he cares," Mueller said. "He's here. He's hustling. He's scoring and putting players in positions to score."

Which isn't to say there haven't been issues.

The ticket market is, uh, out of control, with prices on the secondary market for Sunday's match at LAFC approaching what it would cost to attend every Los Angeles Rams or LA Chargers home game. The Leagues Cup organizing committee priced out Murga 117, an FC Dallas supporter band, due to the exorbitant cost to get into Toyota Stadium, while other Leagues Cup tickets were extreme as well.

"The fact that the supporter section seat -- the $20 ticket -- was initially $300, and then when the full public presale started, it was around $700, is a ludicrous jump in price," Mueller said of the final in Nashville.

The Chicago Fire moved their match against Inter Miami to Solider Field, pumped the ticket prices and will gross more revenue for a single game than for all others on their scheduled combined, according to The Athletic. On one hand, it's hard to say no to that influx of cash. On the other, the cash grab is pretty gross and antithetical to MLS' ethos of consistent, slow and organic growth.

And there's a second drawback, which is that Messi is 36 years old and needs to rest at some point. An injured Messi does no one any good. He didn't start against the Red Bulls and manager Tata Martino said he'll sit at least three times during the remainder of the season. Imagine paying hundreds of dollars for a ticket to see your hometown team host Inter Miami, only for a certain Argentine star to ride the bench.

So yes, his arrival has been messy at times, but really, the Messi Circus couldn't have been expected to go much better. He has breathed new life into away stadiums and broadcasts alike. He has, most importantly, been fun as hell to watch, in person and on television. For a league that wants to grow and needs to grow, he's been nitrogen-enriched fertilizer, giving diehard supporters someone to cheer for and route against, and bringing new fans to the sport.

"Even though we lost, I still think it was a major win for the Philadelphia Union and their fans because we were there to provide entertainment for the night and potentially provide an experience for a kid at his first game," Migliaccio said. "I kept walking around that stadium, seeing the families there, and thinking, 'I hope they remember this as much as much as I do.'

"And who knows? Maybe one day that kid plays for the Union, then goes over to Europe, and becomes the next Messi. And you know why? Because of that one night down in Chester."