Star midfielder Keisuke Honda said Japanese people are not patriotic enough, in comments published on Thursday after a controversial episode at the Olympics last month.
The 26-year-old said he understood why a South Korean player had held up a sign proclaiming sovereignty over disputed islands during celebrations after his team beat Japan to the bronze medal at the London Games.
It is rare for top sportsmen to comment on politics in Japan.
"Putting aside if it's good or bad, I thought he loves South Korea," the CSKA Moscow player told the Nikkan Sports in Moscow ahead of a 2014 World Cup qualifier between Japan and Iraq on September 11.
"I love Japan. If I were in the same position, I might have taken similar action," said Honda, who is now back in Japan for a friendly against the United Arab Emirates later Thursday.
South Korean midfielder Park Jong-Woo was barred from the Olympic medal ceremony after holding up a sign declaring: "Dokdo is our territory" moments after his side beat Japan 2-0 in London.
The incident came amid growing tension over the ownership of South Korean-controlled islands that lie between the two countries, known as Dokdo in Korean and Takeshima in Japanese.
"If I compare the love for one's home country (between Japanese and Koreans) I suspect the Japanese are losing," said Honda, who led the Blue Samurai to the last 16 at the 2010 World Cup and was the most valuable player at the 2011 Asian Cup when Japan clinched a fourth continental title.
Honda, who spent time at J-League outfit Nagoya Grampus and VVV-Venlo in the Netherlands before moving to Moscow in 2010 has a reputation for saying what he thinks, although in the past he has confined himself to football.
Relations between Japan and South Korea went into a tailspin when South Korean President Lee Myung-Bak paid a surprise visit to the disputed islands on August 10, sparking angry protests from Japan.
Japan is also struggling to mend ties with China over another territorial dispute over an archipelago in the East China Sea.