Nery Castillo scored at the 24th minute before Ramon Morales made it 2-0 just five minutes later for underdog Mexico.

In the other Group B match on Wednesday, Chile rallied with two late goals to beat Ecuador 3-2.

Morales scored off a free-kick and Castillo beat a defender before hitting the mark to open the scoring against a depleted Brazil squad which was missing some key players.

Brazil had chances to score in the second half but Robinho's drive sailed off the crossbar.

Substitute Carlos Villanueva was the key as he stepped off the bench with 20 minutes remaining to set up one goal before scoring himself to clinch the victory for Chile.

Mexico coach Hugo Sanchez is confident his side will make it to the semifinals of the Copa America at the very least following their stunning victory.

"I'm not the best or the worst coach, it's simply a line of work. It's the players who made it happen, I direct them. There was no magic formula, just dedication and work."

"The boys played very well and showed that Mexico are one of the most powerful teams on the continent. Mexico will reach the semifinals," said Sanchez.

Goal-hero Castillo was delighted to have defeated one of the best sides in the world.

"Brazil have the best players on the planet and we were better than them because we played good football," said the Olympiacos midfielder.

Brazil coach Dunga reflected: "The team played well but we let in two goals through lack of concentration.

"We created chances but weren't able to capitalise on them. But We're still in with a chance."

"Obviously we'd have liked to have started with a win but we have time to improve."

Real Madrid's Robinho added: "I prefer for the side to play badly and win than play well and lose."

Ecuador had dominated their game and had deservedly broken the deadlock through Antonio Valencia, who collected a pass from Carlos Tenorio before firing home.

In the 19th minute, Colo Colo striker Humberto Suazo equalised with a superb effort from distance, but Ecuador was soon back in front when Cristian Benitez took advantage of an error by Chilean goalkeeper Claudio Bravo to make it 2-1 in the 22nd minute.

Luis Fernando Suarez's side continued to dominate and had chances to further extend their lead but failed to convert any of them.

Chile's Uruguayan coach Nelson Acosta brought on Miguel Riffo and Juan Lorca during the interval in a bid to increase his side's attacking threat and it paid off.

Acosta hailed his side's determination of coming back from behind to win the match.

"Ecuador played better than us for the majority of the game, but in the second half we improved. The players overcame all the difficulties they faced,” said Acosta.

"We did not play well, but to win always helps and gives us confidence."

Midfielder Rodrigo Melendez is confident Chile can go on to make history in the tournament.

"In the first half we controlled the ball, but Ecuador scored in the crucial moments," he said. "But we didn't give up and secured three important points. I believe that this team can make history."

Meanwhile, Ecuador coach Luis Fernando Suarez criticised the Chilean style of play.

"Chile aren't famous for being a team that shows spectacular soccer," he said. "We are a great team, but today we did not play well and that cost us the dearly.

"Today we committed many errors that we cannot repeat if we want to qualify for the next round."

Chile next face Brazil while Ecuador face Mexico on Sunday.