Former FIFA President Sepp Blatter spent a week in an induced coma after having heart surgery last month, his daughter has revealed.
Blatter contracted coronavirus in November before undergoing a heart procedure at a hospital in Switzerland in December.
The 84-year-old was moved out of intensive care this week, but Blatter’s daughter said there was "still a long way to go" in his recovery.
"He makes progress every day," said Corinne Blatter Andenmatten in an interview with Swiss media company CH Media.
"Doctors are happy with his condition but there is still a long way to go.
"It is correct that he tested positive for COVID-19 in November.
"But he survived the virus without any major symptoms.
"But this disease is insidious.
"Maybe my father lost more substance than he wanted to admit.
"Shortly before Christmas he had to go to the hospital for a heart operation.
"He assumed it was a routine operation but then everything got more complicated and dangerous.
"Overall, he was in an artificial coma for over a week and was no longer responsive.
"We were very worried.
"That was the hardest and saddest Christmas time of my life."
Blatter was President of FIFA for 17 years until 2015 when he resigned amid a corruption scandal which led to United States prosecutors indicting several officials.
Blatter is currently serving a six-year ban from football.
FIFA issued a complaint of "criminal mismanagement" against Blatter last month relating to his involvement in the FIFA Museum project in Zurich.
Those accusations were dismissed as "baseless" by Lorenz Erni, Blatter's lawyer.
"He doesn't know anything about the museum lawsuit," said Blatter Andenmatten.
"And that's just as well.
"He would just get upset unnecessarily.
"We keep these negative things away from him for as long as possible."
Blatter Andenmatten also spoke of her anger towards FIFA President Gianni Infantino.
"I hope I never meet him again," she said.
"I would probably lose my temper.
"It cannot be that Infantino takes such a stubborn stance against the man who left a nest for him."
A CHF2 million (£1.66 million/$2.26 million/€1.85 million) payment made by Blatter to former UEFA President Michel Platini in 2011 is still being investigated.
In November, it was reported that Swiss prosecutors had widened proceedings against Blatter and former French international - both of whom have maintained the payment was made as part of an oral agreement for work Platini carried out for Blatter between 1998 and 2002.
FIFA's Ethics Committee dismissed that claim when it banned Blatter from all football-related activities, and its ruling was later upheld by the Court of Arbitration for Sport.
Blatter Andenmatten suggested the legal cases were having an impact on her father’s health.
"I am not a doctor - and neither am I a psychologist," said Blatter Andenmatten.
"But if you consider what my father has had to put up with in the last five years, what previous convictions - without a state court having pronounced a judgment against him - you can imagine that he was under great pressure."
Blatter Andenmatten said her father deserved to enjoy the rest of his life without being "constantly torpedoed" by FIFA and urged the worldwide governing body to leave him alone.
"I vehemently appeal to leave my father in peace and give him what he needs on the way to a hospital complete recovery of rest, time and relaxation," she added.