The Sporting Lokeren defender Gregory Mertens has died in hospital, three days after he collapsed during a reserve match.
The 24-year-old, who had played for Belgium at Under-21 level, had been in a coma since going into cardiac arrest early in a game against Genk on Monday night.
The Lokeren spokesman Herman Van de Putte said Mertens' condition continued to worsen and the player's family had agreed with doctors to switch off the life support system.
Mertens began his senior career at Cercle Brugge in 2011 before he made the move to Lokeren in January last year. He made his debut as a late substitute in a 3-0 victory over his former club on 18 January 2014 and made 30 further appearances for the first team, including three Europa League games earlier this season.
A club statement said: "Today something happened which no one could ever dare to predict. Much too soon, we are saying goodbye to Gregory Mertens.
"We are a football club. Everyone in and around the club lives and breathes football. But suddenly something happens which makes us realise football is just football. Today is such a time."