Bolton midfielder Fabrice Muamba is "critically ill'' in intensive care at the heart attack centre of the London Chest Hospital, the club have confirmed.
After being treated by six paramedics, Muamba, 23, was rushed to hospital where a spokesman earlier told Sky sources he was in a stable condition after medical staff managed to restore his breathing.
However, the club have now released a statement which read: ''Bolton Wanderers can confirm that Fabrice Muamba has been admitted to the heart attack centre at London Chest hospital where he is currently in a critically ill condition in intensive care.
''No further information will be issued at this stage. The club has requested the media to respect his family's privacy at this time.''
Bolton manager Owen Coyle accompanied Muamba to the hospital and later emerged to give an update on the player's progress.
He told Sky News: "Fabrice is critically ill. The next 24 hours are going to be absolutely crucial.
"We've obviously been inundated with people wishing him well and we hope that if everybody can pray strongly tonight that Fabrice is able to recover.
"It's very serious. There's not getting away from that. He's critically ill and God willing he makes it through."
Many of the players on the pitch were visibly distressed and Rafael van der Vaart, who started the game for Spurs, wrote on Twitter: ''Terrible what happened with Muamba during the game. We're all praying for him.''
And striker Emmanuel Adebayor, who missed the game with a hamstring injury, added: ''My thoughts are with Fabrice Muamba's family. We all are praying for him and hope for a speedy recovery.''
FA Chairman David Bernstein said: "On behalf of The FA, I would like to send our thoughts and prayers to Fabrice Muamba and his family this evening.
"Fabrice has played 33 times for England Under-21s, captaining Stuart Pearce's side during this time and is a player, and more importantly, a person we care greatly for. We are in contact with Bolton Wanderers over Fabrice's condition and are awaiting updates."