European champions Paris Saint-Germain suffered a shock 1-0 Club World Cup defeat to Brazilian side Botafogo on Thursday after Lionel Messi lit up the tournament with a brilliant free-kick winner for Inter Miami.
Atletico Madrid and Palmeiras also won as the second round of group matches began, but it was Botafogo who stole the headlines.
A first-half goal from Igor Jesus proved the difference as last year's Copa Libertadores winners all but sealed a place in the knockout rounds from Group B in front of 53 699 fans at the Pasadena Rose Bowl in California.
PSG are one of the favourites for Fifa's 32-team tournament after a dazzling season which culminated with a scintillating 5-0 demolition of Inter Milan in the Champions League final.
But their hopes of securing a victory which would have seen them become the first side into the last 16 were stymied by a resilient performance from their opponents from Rio de Janeiro.
"A lot of people wondered, but we showed how strong Botafogo is," goalscorer Jesus said after the win, which kept all of South America's representatives unbeaten at the competition in the United States.
"It was a difficult game and we had to defend well, and we did our job and scored a goal."
Botafogo took the lead against the run of play on 36 minutes as Jefferson Savarino's through ball split the PSG defence and released Jesus.
He then did brilliantly to wrongfoot the covering Willian Pacho before sweeping a shot that took a slight deflection past goalkeeper Gianluigi Donnarumma on its way into the net.
"We knew it was going to be a very difficult match – they defended very well," said PSG coach Luis Enrique.
"This Club World Cup is very intense and difficult and all the teams are highly motivated, especially when they're playing against us."
Botafogo's win leaves them firmly on course for the last 16, with a final group game against Atletico to come on Monday.
ATLETICO OFF THE MARK
Atletico bounced back from a 4-0 loss to PSG as Diego Simeone's side beat Seattle Sounders 3-1.
Pablo Barrios scored twice, including an 11th-minute opener which crashed in off the underside of the crossbar.
Belgian Axel Witsel came off the bench at halftime and almost immediately made it 2-0, nodding in from close range after a Marcos Llorente shot was tipped onto the woodwork.
Albert Rusnak quickly pulled one back for Seattle, only for Barrios to score again for 3-1.
Botafogo top Group B with six points, with PSG and Atletico each on three and Seattle facing probable elimination after two defeats.
Earlier, Messi scored a trademark free-kick to secure a 2-1 comeback win for Inter Miami against Porto in Atlanta in Group A.
The Argentine superstar found the top corner with a set-piece nine minutes after halftime to clinch a surprise victory for the MLS side and give them a strong chance of progressing.
Samu Aghehowa's early penalty gave Porto the lead and they had the better of the first half.
But Telasco Segovia blasted Miami level and then Messi's free-kick helped them claim a noteworthy scalp.
"It's a huge joy, the whole team made a big effort, we worked really well," Messi said.
"It's a really important win for us and we have to enjoy it.
"You can see that we want to compete and today we competed against a really good European team."
Javier Mascherano's Inter Miami have four points from two games, meaning they are level atop the group with Palmeiras.
The Brazilians beat Egypt's Al Ahly 2-0 at MetLife Stadium outside New York.
A Wessam Abou Ali own goal gave Palmeiras a 49th-minute lead before Flaco Lopez doubled their advantage 10 minutes later.
The match was then suspended in the 63rd minute because of a weather warning, with players and fans instructed to take shelter because of a nearby storm before the action eventually resumed.
A draw between Inter Miami and Palmeiras on Monday will send both teams into the last 16.