The tenacious defender played more than 360 top-flight games for Yokohama F. Marinos and was one of the most popular players of the J. League era. He joined third-tier side Matsumoto Yamaga after being released by F. Marinos at the end of last season.
Once a mainstay of the Japanese national team, Matsuda started all four of Japan's games on home soil at the 2002 World Cup.
He was rushed to hospital after suffering a cardiac arrest before afternoon training with his new club.
Doctors are yet to determine the cause of Matsuda's condition, although Japan has experienced heatwave conditions for much of the summer.
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