Former Japan international Naoki Matsuda died in hospital on Thursday at the age of 34.
His death comes two days after collapsing from a suspected heart attack during a training session with his club Matsumoto Yamaga.
It was reported the player had initially collapsed with heatstroke and then later slipped into a coma.
The defender won 40 caps for Japan and represented his country at the 2002 World Cup. He also made 385 appearances for Yokohama F-Marinos, helping them win back-to-back J.League titles in 2003 and 2004.