FORT LAUDERDALE, Florida: Lionel Messi walked off the field and into the tunnel leading to the Inter Miami locker room a few seconds after the final whistle blew, hardly any emotion on his face.

He didn’t want to see the celebration.

Atlanta United ousted Messi and Major League Soccer’s biggest-spending team earlier than anyone imagined from the MLS Cup playoffs. Jamal Thiare scored twice, Bartosz Slisz’s header in the 76th minute was the winner, and Atlanta United stunned Inter Miami 3-2 on Saturday night to win their best-of-three first round playoff series in three games.

“There’s some fairy dust in our locker room, man,” Atlanta United goalkeeper Brad Guzan said after stopping seven shots, some of them in spectacular fashion, and giving Slisz a big hug in response to his goal. “I couldn’t be more proud of our guys.”

Two free kicks by Messi in the final minutes hit the wall of Atlanta defenders, and time eventually ran out on soccer’s most decorated player and his team. Messi’s header — yes, header — in the 65th minute tied the match at 2-2, but the hosts never reclaimed the lead. Atlanta took the lead with an Inter Miami player down and the hosts lobbying for play to be halted, but the whistle never came and Slisz became one of many heroes for the winners.

“It’s everybody. It’s a joint effort,” Atlanta United interim coach Rob Valentino said. “We talked about it before the game, we talked about it all year long that it’s not going to be just one player. It’s a collective effort and that’s what happened tonight.

It was the fifth win-or-else victory for Atlanta United this season — starting with two must-win matches to keep hope alive at the end of the regular season against the New York Red Bulls and Orlando City, then a wild-card match at Montreal, Game 2 of this series at home and then Saturday’s stunner.

And the East is suddenly wide open.

Ninth-seeded Atlanta United will play No. 4 Orlando City in the Eastern Conference semifinal, while sixth-seeded New York City FC will face the seventh-seeded New York Red Bulls in the other East semifinal.

No. 2 Columbus was already gone. No. 3 Cincinnati was ousted Saturday. And then came the biggest surprise of all — No. 1 Inter Miami’s season is over.

“Once you get in, this league is like this,” Valentino said. “You’ve got to have that belief in yourself because nobody on the outside is going to believe in you.”

The team with the best record won the MLS Cup four times in the league’s first seven seasons. In the 22 seasons since, the top overall seed has gone on to win the title only four more times.

And on paper, there may never have been a bigger upset than this one — a No. 9 seed vs. a No. 1 seed, and not just that, a No. 1 seed with Messi in the lineup. Messi’s $20,446,667 in total compensation from Inter Miami this season was about $5 million more than the entire Atlanta payroll, and Inter Miami spent a record $41.7 million on payroll this season.

It got Inter Miami the Supporters’ Shield, the best regular-season record in MLS history and an invitation to next year’s Club World Cup, which came as no surprise. But it didn’t even get the club into Round 2 of the playoffs, which will be remembered as a massive flop.

“Our biggest objective, we didn’t manage,” Inter Miami coach Gerardo “Tata” Martino said.

Atlanta United fully believed it was going to pull this off.

For whatever reason, Atlanta was a matchup nightmare for Inter Miami this season. It beat Inter Miami three times, all of them with Messi in the lineup; every other MLS team combined to get three wins over Inter Miami.

A five-minute, three-goal barrage in the first half set the tone. Inter Miami opened the scoring and Atlanta United punched right back — twice.

Thiaré was denied by the goalpost 14 minutes into the contest, when his deflection of a flick into the box narrowly missed. And Inter Miami grabbed a 1-0 lead about two minutes later — Messi was stopped by a diving Guzan, but Matías Rojas was there to lift the rebound into the net from a tight angle near the right post.

The lead didn’t last long. Thiaré saw to that.

He took a pass and was completely unmarked, firing into the upper right corner to beat Inter Miami goalkeeper Drake Callender — who had no chance — to tie the match in the 19th minute. And not even two minutes later, Alexey Miranchuk tapped a pass to Thiaré who went over Callender for a 2-1 Atlanta lead.

Just like that, the best team in MLS regular-season history — and the best player in the sport’s history — was in big, big trouble. Inter Miami thought it tied the match in the 25th minute, only for Diego Gómez to be called offside. And the hosts argued wildly for a penalty kick later in the half, arguing that there was a handball in the box (replay suggested they had a case), but they still went into the half down 2-1.

“A very clear penalty,” Martino said. “The ref didn’t even check it.”

Messi tied it midway through the second half, no one knowing at the time that it would be the final hurrah for Inter Miami’s season. For some reason, Inter Miami’s pyrotechnics crew shot fireworks off as time expired, as if the team was celebrating something.

On this night, it was Atlanta United that sent Inter Miami’s season up in smoke.

“I hope we’re not done now,” Valentino said.