Bolton's Fabrice Muamba remains in a critical condition in intensive care at the London Chest Hospital.
The midfielder, 23, was taken to the heart attack centre at the hospital after collapsing during Saturday's FA Cup quarter-final tie at Tottenham.
A joint statement from the club and hospital on Sunday said: "As is normal, he remains anaesthetised in intensive care and will be for at least 24 hours.
"His condition continues to be closely monitored by the cardiac specialists."
Bolton manager Owen Coyle added: "Fabrice's family have asked me to pass on their thanks for the many, many kind messages of support from not only Bolton fans but also fans from clubs across the country and abroad.
"All our thoughts and prayers are for Fabrice and his family at this time. The family would also like to thank the media for respecting their privacy at this time."
Coyle had earlier said: "It's very serious. There's no getting away from that. God willing, he makes it through."
Medics spent six minutes trying to resuscitate the former England under-21 international on the field after he fell to the ground with no other players around him.