Bolton Wanderers doctor Jonathan Tobin has revealed that Fabrice Muamba was "in effect dead" for 78 minutes following his cardiac arrest on Saturday evening.
After medical staff worked to restart the 23-year-old midfielder's heart on the White Hart Lane pitch for around 30 minutes, he was taken to the London Chest Hospital in Bethnal Green.
Over the past 72 hours Muamba's condition has improved, something that Tobin has described as "incredible".
"It was 48 minutes when he collapsed to reaching hospital and a further 30 minutes after that. He was, in effect, dead at that time," Tobin told BBC Sport.
"We were fearing the worst and didn't think we would get the recovery we had. It's incredible."
Doctors have said that it is too early to predict whether Muamba will play football again.