The former Manchester United player's son by his first marriage, Calum, joined his critically ill father at the Cromwell hospital in west London during the day. Roger Williams, his long-term doctor who oversaw Best's liver transplant in 2002, said the 59-year-old was sedated and on a life-support machine. He has been unconscious since Wednesday morning.
Best was admitted to hospital nearly four weeks ago with an infection, and his condition has since deteriorated.
Phil Hughes, Best's agent, said last night the infection had spread from his chest to his kidneys and was also affecting other organs, adding that his condition was "as bad as it gets".
The agent said Best, who played for Northern Ireland and is regarded by many as the most talented player Britain has produced, has not been well enough to contact any friends or family directly.
He said: "I texted a couple of his close friends but apart from Calum and his brothers and sisters, George hasn't contacted anyone."
Professor Williams told Best's son that the next 24 hours were crucial; his father's condition may deteriorate and he is unable to breathe without the help of a ventilator.
"He wasn't in good spirits. He was very depressed, but is still fighting away, as he always does. We are just hoping we can control the bleeding," Professor Williams said.
Patients in intensive care for long periods often develop problems with internal bleeding.
"All one can say is that the bleeding, we think, is easing - but he is very seriously ill on a ventilator. Quite what will happen over the next 24 hours is difficult to say. He could pull through or he could get worse," the professor said.
Professor Williams said the internal bleeding of the bowel had been linked to an infection, and treating it with antibiotics could have risked making things worse.
The current illness is not directly linked to his replacement liver, which has been functioning well. According to the professor, Best will not be taken off the ventilator "until we are sure that he is breathing on his own".
But he said there was "no intention to withdraw treatment" though it is impossible to "have a clear idea [of the prognosis] when people are as sick as this". He added: "You go from day to day with all the expertise you can."
The former England footballer Paul Gascoigne, who has fought his own public battle with alcoholism, said his thoughts were with Best. "It was a shock to me last night and I admit I didn't sleep at all thinking about him. I've been through the same but not as bad as what George has." Speaking at Kettering Town Football Club, where he will become player-manager, Gascoigne added: "Of course my thoughts are with him. I hope he pulls through this."
Best's former wife, Alex, said she had been told his condition had "deteriorated dramatically". She said: "I am just praying that, once again, he somehow manages to pull through against all the odds. My thoughts and prayers are with him." Best's latest health problems are thought to be related to immuno-suppressant drugs he has been taking since his transplant to stop the organ being rejected. The former footballer, who had his life-saving liver transplant at the hospital, caused anger when he embarked on a drinking binge within months of his liver transplant operation in July 2002. He had been told one more drink could kill him.Reuse content