Lokeren defender Gregory Mertens is in a critical condition after suffered a suspected cardiac arrest during a match.
Former Belgium under-21 international Mertens was representing Lokeren's reserve side in a game against Genk on Monday when he collapsed and received CPR on the pitch.
- Sporting Lokeren (@KSCLokeren) April 27, 2015
A statement on the club's official website said that, after the 24-year-old collapsed, he was given treatment by both clubs' medical teams before being transferred to a hospital in Genk.
The club added: "Sporting Lokeren sympathises with the family and hopes for a positive outcome."
Het Laatste Nieuws reported that he had been placed into an artificial coma, and the Belgian newspaper quoted club doctor Kris Peeters as saying: "All signs point to a cardiac arrest. I am in constant communication with the physicians treating him in Genk. The condition of Gregory is still critical."
Peeters added on RTL's website: "The exact cause of the problem is not known, and we will have to do extensive tests, but it seems more than likely that it is a heart attack.
"Gregory Mertens' heart has undergone extensive tests. We always do that at the club, and it's necessary to be able to play in the Europa League. This very unfortunate incident could not have been predicted. Gregory Mertens is a elite athlete and is only 24 years old. That makes things difficult to accept and to understand for a lot of people."
A host of leading Belgian players offered Mertens their support on social media.
Chelsea goalkeeper Thibaut Courtois and Everton striker Romelu Lukaku both urged the player to "keep fighting."
Blijven vechten Gregory! #bestrong ����
- Thibaut Courtois (@thibautcourtois) April 27, 2015
Blijf vechten gregory!!
- R.Lukaku Bolingoli10 (@RomeluLukaku9) April 27, 2015
Liverpool goalkeeper Simon Mignolet sent out the same message.
My thoughts are with you Gregory ! Keep fighting ! #GregoryMertens
- Simon Mignolet (@SMignolet) April 28, 2015
Peeters said that Lokeren's training session on Tuesday morning had been cancelled but that he would speak to the players to give them an update on Mertens' condition.