Brazil was high on confidence after a 5-0 thrashing of South Korea on Friday, but Japan brought it back to earth with a stunning comeback to seal a dramatic 3-2 victory.

Paulo Henrique and Gabriel Martinelli had given the Selecao a 2-0 lead, but Takumi Minamino, Keito Nakamura and Ayase Ueda all scored within 19 second-half minutes to flip the game on its head.

Before the match, Japan had failed to win any of its previous nine meetings with Brazil, losing seven and drawing two.

Ancelotti was disappointed with his side's reaction after conceding the first Japan goal, calling for his players to improve their mentality.

"Individual mistakes don't affect a player's presence on the team," Ancelotti said about their defensive errors.

"What we have to evaluate is the team's reaction after the first mistake, which wasn't good because we lost some of our balance on the field and our positive thinking. We have to learn from our mistakes in the second half.

"The team's biggest mistake was not reacting well after the first goal. It's a good lesson for the future. We have to learn from this defeat.

"I think until Fabrício's mistake [in the first goal] we controlled well the game. The team then lost its mentality after the first mistake. That was the team's biggest mistake.

"We'll continue doing tests during the FIFA window in November. This doesn't change our approach. I think we need to be balanced in what we do.

"The team played very well against South Korea, played well in the first half [against Japan], and very poorly in the second half. It's a process, and in the World Cup, we need balance."

Brazil captain Casemiro was also frustrated at full-time, noting how costly their mistakes could be if they were made on a big stage.

"A second-half blackout by the entire team," Casemiro said. "If you sleep for 45 minutes, it could cost you a World Cup, a Copa America, a medal, a four-year dream.

"The whole team wasn't at its best in the second half, and it's the details. At this high level, it's the details that make all the difference. We know there was an extra boost of enthusiasm [following the win against South Korea].

"We wanted to end this 12-day preparation on a high note. And perhaps we threw away our excellent preparation in 45 minutes. So, let this be a lesson learned: the World Cup is here. We need to play at a high level, no matter if it's against Japan or whoever, as 45 minutes can cost you a childhood dream."