George Best remains critically ill on a life support machine and the next 24 hours are crucial for his survival, his doctor Professor Roger Williams said on Sunday.
"Going on like this without improving is I think disappointing and we're very worried about his condition overall," Williams told reporters outside the Cromwell hospital in London.
"We would like to have seen him make some very definite improvement.
"The next 24 hours is very critical for Mr Best as to whether he is going to survive this infection and all the consequences of it on his body."
The hospital had earlier said Best was critical but stable.
The former Manchester United winger, one of the finest players in soccer history, has been in hospital since the beginning of October. He underwent a liver transplant in 2002 after years of heavy drinking.
On Sunday, a picture of Best looking gaunt and yellow was published on the front page of the mass-selling tabloid News of the World with a message saying: "Don't Die Like Me".
The paper said Best had asked for it to be published as a warning to others about the dangers of excess drinking.
"George could never beat his drink problem, but he told me 'I hope my plight can act as a warning to others,'" Best's agent and friend Phil Hughes told the paper.
The former Northern Ireland international, 59, was initially admitted to hospital after having a reaction to the treatment he was receiving for his new liver and then suffered internal bleeding linked to a bowel infection.
After initial warnings that Best was close to death, his condition improved although he remained in hospital.
On Friday he was readmitted to intensive care with a lung infection.
The 1968 European Footballer of the Year has had an alcohol problem for much of his adult life.
