European champions Paris Saint-Germain lost 1-0 to their South American counterparts Botafogo on Thursday night at the Club World Cup.
Igor Jesus scored the winner just before half-time at the Rose Bowl in Pasadena.
The 24-year-old latched onto Jefferson Savarino's through ball, held off PSG defender Willian Pacho before sweeping a shot past goalkeeper Gianluigi Donnarumma.
PSG thrashed Atletico Madrid 4-0 in their opening game at the tournament but their strikers failed to respond to the setback.
"We knew it was going to be a very difficult match," said PSG coach Luis Enrique. "They defended very well. This Club World Cup is very intense and difficult and all the teams are highly motivated, especially when they're playing against us."
Botafogo, who claimed the Copa Libertadores last November, moved to the top of Group B with six points after two games.
PSG lie second with three points following their first defeat since annihilating Inter Milan 5-0 to lift the Champions League crown.
"A lot of people were wondering about how good we are," said Jesus after the victory. "But we showed how strong Botafogo is. It was a difficult game and we had to defend well and we did our job and scored a goal."
On Monday, Botafogo play their last tie in the pool against Atletico Madrid who bounced back from their defeat to PSG with a 3-1 win over Seattle Sounders at Lumen Field in Seattle.
Pablo Barrios scored the opener for Atletico after 11 minutes and Axel Witsel doubled the advantage just after the pause.
Albert Rusnak quickly halved the deficit but Barrios struck his second goal of the night and Atletico's third in the 55th minute.
Atletico can advance to the last-16 with a draw against Botafogo if PSG lose on Monday night against the Seattle Sounders.
Another Messi special
In Atalanta in Group A, seven-time Ballon D'Or winner Lionel Messi produced a trademark free-kick into the top right hand corner of the goal to take Inter Miami to a 2-1 win over Porto.
Samu Aghehowa gave the Portuguese outfit the lead from the penalty spot eight minutes into the tie at the Mercedes Benz Stadium.
Telasco Segovia got the equaliser for Inter Miami after 47 minutes and Messi provided the pyrotechnics seven minutes later.
"It's a huge joy," Messi told broadcaster DAZN. "The whole team made a big effort and we worked really well, It's a really important win for us and we have to enjoy it. You can see that we want to compete and we competed against a really good European team."
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.
