RIO DE JANEIRO - The overwhelmingly Brazilian crowd at the Rio Olympics roared and danced when the decision was announced -- their boxer had narrowly won on points and in return he blew kisses.

For the Brazilians watching the Rio boxing, it is case of anyone but an Argentine or an American.

So they hailed the flyweight Daniel Asenov as one of their own on Saturday when he defeated Fernando Martinez from Argentina, Brazil's great rival.

Similarly, on Friday, they booed the American Mikaela Mayer out of the arena after she easily beat Jennifer Chieng, representing Micronesia.

And they gave Chieng a resounding send-off -- presumably unaware that she was born in the United States and lives in Brooklyn.

American flyweight Antonio Vargas, 19, was up against a fiercely anti-American and partisan crowd, and a Brazilian boxer nearly twice his age, on Saturday.

"It is hard with all the noise. You hear the atmosphere, the crowd and the stage rumbling so it was hard for me to keep my cool," the teenager said after a well-deserved points victory.

"I can say that's one of the first fights where I felt nervous, being in his backyard and hearing his fans was like, 'Wow, man, I've got to pick it up.'"