Florentina star Davide Astori, 31, dies in his sleep at team hotel ahead of their fixture with Udinese as all Serie A games are postponed.
Astori, a 31-year-old Italy international central defender, had been with the club since 2016 having previously played for Milan, Cagliari and Roma.
He had 14 international caps with Italy and was a member of the squad that played in the 2013 FIFA Confederations Cup.
All of Sunday’s Serie A fixtures have been postponed as a mark of respect.
One report from Italy said his team-mates broke down his door when Astori failed to come down for breakfast or answer his phone.
‘The lad did not turn up to the team breakfast at 9.30am and he was usually the first to arrive,’ said Fiorentina spokesman Arturo Mastronardi.
‘So they went to check on him. Davide was sleeping in a room on his own. We still don’t know the cause of death. The Magistrate came here and the body has been taken for an autopsy, which I think will be conducted today. We have no further details.
‘The last to see Davide was Marco Sportiello. Some players sleep in single rooms, some in doubles.
‘His family is from Bergamo, so his parents were alerted by telephone, whereas his partner was visited in person in Florence by some of the directors who were in the city.
‘The team will return to Florence today with a charter plane.’
Astori leaves a wife Francesca and two year old daughter.
A statement issued by Fiorentina read: ‘Fiorentina are profoundly shaken and forced to announce that their captain Davide Astori has died.
‘For this terrible and delicate situation, and above all out of respect for his family, we appeal to the sensitivity of the media.’
Italy legend Gianluigi Buffon and Chelsea boss Antonio Conte led the tributes to Astori.
Buffon wrote on Instagram: ‘You have a young wife and family members who are suffering. Your little girl deserves to know that her father was in all respects a perfect person.
‘You were the best expression of an ancient, surpassed world, in which values such as altruism, elegance, education and respect for others, were the masters.
‘You were one of the best sports figures I ever came across.’
Conte, speaking on Sky ahead of Chelsea’s game against Manchester City, was clearly upset and said: ‘I had him with the national team. It is very hard in this moment to speak about this tragedy.
‘He was a fantastic guy. He was a great player but especially a fantastic guy. He was only 31. It is very difficult to explain this situation, his wife, the parents, the daughter.’
Astori, who hailed from the province of Bergamo, started playing with local team Pontisola before joining Milan’s academy in 2001.
He spent five years in their youth system, including loan spells at Serie C1 clubs Pizzighettone and Cremonsese in the 2006-07 and 2007-08 seasons.
Astori didn’t turn out for the senior Milan side and signed for Cagliari in a co-ownership deal with Milan in 2008, playing regularly for them in Serie A.
In all, Astori made 178 appearances for Cagliari during six seasons before moving out on loan to Roma at the start of the 2014-15 season.
When he returned to Cagliari, Fiorentina also took him on loan before completing a permanent transfer in 2016.
Astori was expected to sign a new contract with the club when he died.
He made 14 appearances in all for Italy having been handed his debut by coach Cesare Prandelli against Ukraine in March 2011, though he was sent off during that friendly match.