Bolton Wanderers footballer Fabrice Muamba remains in a critical condition in intensive care after suffering a cardiac arrest.
The player's fiancee urged fans to pray for him, while the club's manager Owen Coyle said he hoped there would be a "happy outcome" for Muamba.
It has emerged that paramedics could not get the 23 year old's heart to start beating on its own for almost two hours after he collapsed on the pitch during an FA Cup tie.
He fell to the ground at White Hart Lane at 6.11pm on Saturday in front of millions of television viewers watching the club's quarter final clash with Tottenham Hotspur.
Paramedics desperately tried to resuscitate him but were unable to start his heart working by itself again until he reached London Chest Hospital, in Bethnal Green, east London, at 8pm.
He remains in a critical condition and is anaesthetised in an intensive care unit at the hospital which is seven miles away from the stadium.
Muamba's fiancee, who goes by the name Shauna Muamba on Twitter and is mother to their son Joshua, told fans on the social networking site:
She later added:
Another post said:
She tweeted on Valentine's Day that she had accepted the player's proposal.
After visiting Muamba in hospital, Coyle said: "From our end, and on behalf of the family, we certainly want to say thanks to everybody.
"Everybody is praying for Fabrice which is very important and that has been a real source of strength to the family.
"It's great to be talented at football but it is more important to be a genuinely nice man and Fabrice is that.
"Our concern is Fabrice and Fabrice only and that's what all our energy is going into - hopefully a happy outcome."
Relatives, including Muamba's brother and fiancee, and colleagues have visited the hospital since he was admitted.
Coyle has attended the hospital twice and chairman Phil Gartside arrived yesterday flanked by two other men.
After Gartside left he said: "The support that we had yesterday from Tottenham and our own fans was fantastic - the staff, the fans, the players and the officials at the game - it was unbelievable.
"We have had so many messages of support from around the world."
He later released a statement on the club website, extending his thanks to hospital staff and the "global footballing family".
He hailed staff at the hospital as being "nothing short of exceptional".
Muamba's friend, Arsenal defender Johan Djourou, and Spurs striker Jermain Defoe, who was in tears on the pitch seeing Muamba lying on the floor, also visited.
Defoe stayed for just 15 minutes and was too upset to comment as he left. Djourou was seen walking out of the hospital grounds later, after avoiding the waiting camera crews as he left the building.
Meanwhile, Wanderers have postponed their next fixture. The Premier League tie against Aston Villa was due to take place on Tuesday evening, but a statement on the club's statement said the match had been called off.
During several games yesterday, including Manchester United's Premier League clash with Wolverhampton Wanderers and Newcastle's game against Norwich, players and fans showed their support for Muamba with a minute's applause before kick off.
During Chelsea's 5-2 FA Cup quarter final victory over Leicester City, former Bolton player Gary Cahill lifted his shirt to reveal a "Pray for Muamba" T-shirt after he scored the London club's first goal.
Since the incident, fellow players have taken to Twitter to express their shock.
The Trotters midfielder fell to the floor in front of a packed stadium on Saturday.
Shocked players and fans watched as the former England under-21 star was treated with a defibrillator for several minutes before being stretchered off wearing an oxygen mask.
World Cup referee Howard Webb abandoned the game and Muamba was treated at the stadium before being taken to hospital, accompanied by Coyle and Wanderers' captain Kevin Davies.
The hospital said: "Fabrice Muamba remains in a critical condition in intensive care in the Heart Attack Centre at the London Chest Hospital.
"He was admitted to the hospital yesterday evening after collapsing at White Hart Lane where he sustained a cardiac arrest during the FA Cup quarter final against Tottenham Hotspur.
"Fabrice received prolonged resuscitation at the ground and on route to the London Chest Hospital where his heart eventually started working.
"As is normal medical practice, Fabrice remains anaesthetised in intensive care and will be for at least 24 hours. His condition continues to be closely monitored by the cardiac specialists at the hospital."
Fans have left a series of tributes, including cards, a flag and football shirts, to Muamba outside the hospital and at Bolton's Reebok Stadium.
Muamba was also wished a full recovery by England cricket team director Andy Flower, who revealed the ECB's medical staff detected a heart problem in a young player in 2010.
Mr Flower, who is in Sri Lanka ahead of his side's forthcoming Test series, said the England squad's thoughts were with the 23-year-old.
He also explained how regulation screening picked up a problem on Somerset's Calum Haggett, who had been due to play in the Under-19 World Cup two years ago, but subsequently had to undergo heart surgery.
"Our thoughts and sympathies and our feelings are with that young man (Muamba) and we hope that he recovers," said Mr Flower.
"These things, unfortunately, do happen. Our lives as professional sportsmen are very cosseted in all sorts of ways and on the medical front our guys have cardiac screening.
"Hopefully any problems or defects that are serious will be picked up early.
"In fact, we had a case with one of our very young cricketers recently that was picked up very early."
Haggett eventually made a full return to cricket and played three Twenty20 matches for Somerset last year.