Singapore - Japan boss Javier Aguirre hit back on Monday at claims his team lack passion as the Blue Samurai plot to become the first side to score against Dunga's new-look Brazil.
The reigning Asian champions have yet to find form and they needed a Nyron Nosworthy own goal to beat Jamaica last week for their first win in three games under the Mexican.
But Aguirre, speaking before Tuesday's sell-out friendly in Singapore, said the slow start had nothing to do with a lack of commitment.
"I don't agree at all," Aguirre told reporters at Singapore's new national stadium. "For the last three games, it's not true that we didn't play with passion.
"If you're saying we didn't play well, maybe we can argue about that. But whether we had passion or not, there's no question.
"Tomorrow's game is going to be very tough and I'm sure we'll play with determination, don't worry about that."
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Aguirre said he would change six players for the game against Neymar-led Brazil as he hurries to form his squad for Japan's Asian Cup defence in January.
While Japan have also lost to Uruguay and drawn with Venezuela under Aguirre, resurgent Brazil have yet to concede a goal in their three wins since Dunga took charge post-World Cup.
"Brazil have lots of world-class talent and it's going to be a great experience for us. I want us to demonstrate our own strength and we can't wait to show everyone," Aguirre said.
"Brazil have had three wins and it's going to be a tough match, especially as they haven't let in a goal yet. So in tomorrow's game we would like to stop that."
Aguirre did not specify which players he would change but he is already missing Borussia Dortmund play-maker Shinji Kagawa, who suffered a head injury against Jamaica on Friday.
"This is exactly what I wanted, to test them in a difficult situation," Aguirre said. "We have no home games in the Asian Cup and I wanted to play a team which is really tough to beat."
In 10 attempts Japan have never beaten the five-time world champions. But they may find an ally in a pitted and sandy Singapore pitch which looks unlikely to aid slick play.
"It's quite sandy so it may be a bit difficult to show the best performance," said Aguirre.