The Manchester United midfielder felt his national side were some way behind the best teams in the world, but pledged that they would recognise their mistakes and improve
The Asian champions were considered to have a chance of making an impact in Brazil, but they collected just one point to finish bottom of Group C.
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And Kagawa reflected that his team still fell short of the elite in Brazil.
"We can play well as a team, but in terms of individual quality, we are not good enough to score or avoid conceding in the final moments, which is the difference between us and the best teams in the world," the Manchester United man told reporters.
"We actually conceded when we had to try not to, and couldn't finish it when we needed to score against Greece. I think that made a very big difference.
"I would like to get it right so as to improve."
Asked about winning a place in the United starting line-up under Louis van Gaal, Kagawa said he was yet to think about it as he recovers from the disappointment of the World Cup.
"Firstly I have to reflect on this World Cup," he said.
"This is not the end of my career, so I want to make the best of this frustration and disappointment for the sake of my future career."