A visibly shaken Antonio Conte and World Cup winner Gianluigi Buffon paid emotional tributes to Davide Astori, who died at the age of 31 on Sunday, describing their Italian compatriot as "fantastic" and "a great guy".
Fiorentina and Italy international defender Astori was found dead from a suspected heart attack in his hotel room in Udine where his team was staying ahead of Sunday's scheduled Serie A game with Udinese.
Astori leaves behind a wife and a two-year-old daughter.
Conte, who coached the defender when he was in charge of the Italian national team, said the player's death was a "tragedy".
"This is a tragedy and it really hurts me. It's very difficult at this moment to find the right words for the family," Chelsea coach Conte told Sky Sports ahead of his team's Premier League match at Manchester City on Sunday.
"I had him with the national team. He was a great player but especially a fantastic guy. I stay close to his wife, parents and daughter. He was only 31 and it's very difficult to explain this situation."
Veteran Buffon, the Juventus captain, called Astori "a great man".
"Farewell dear Asto", wrote Buffon in a post on Instagram accompanied by a photo of the two players exchanging pennants before a game between their clubs.
Buffon said he did not usually make a habit of expressing his feelings about others.
"I want to make an exception to my rule because you have a young wife and others close to you who are suffering, but mostly because your little girl deserves to know that her dad was a good man... a great man."
Fiorentina's game was called off in the morning. The early kick-off between Genoa and Cagliari, one of Astori's former clubs, was abandoned when players learned the news while warming up on the pitch.
The other five Serie A matches scheduled for Sunday, including the Milan derby, were also cancelled as a mark of respect.
"Fiorentina are profoundly shocked to have to announce the death of captain Davide Astori after a sudden illness," the Serie A club said on Twitter.
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Astori died of "natural causes" after a "cardiac circulatory collapse" -- a type of heart attack -- Antonio de Nicolo, a Udine magistrate was quoted in Italian media as saying.
The magistrate added that it was "strange that such a thing happened without any warning symptoms in a profession which is so closely monitored".
Astori's body was taken to a hospital in Udine for an autopsy.
Astori began his career at AC Milan, also playing for Cagliari and Roma before joining Fiorentina in 2015. He played 14 times for Italy.
He made his international debut under coach Cesare Prandelli in March 2011 as a first-half substitute in a 2-0 victory over Ukraine in Kiev before getting sent off with 17 minutes remaining.
Day of mourning declared
Astori scored his only international goal in the 2013 Confederations Cup third-place play-off against Uruguay, giving Italy a first-half lead in a match which finished 2-2. Italy went on to win on penalties.
"A man who loved football and who grew up as footballer with us. #ACMilan are shocked by the passing of Davide #Astori. It is with great sadness that we offer our deepest condolences to his family and close ones and to ACF Fiorentina," tweeted Milan, Astori's formative club.
Radja Nainggolan, a Belgian international who played with Astori at two clubs, posted a photo of the two of them joyously celebrating a goal at Cagliari.
"A great player, but an even bigger man, so many battles fought together in Cagliari before coming to Rome, I cannot believe it," he wrote.
Italy, who failed to qualify for the World Cup, are due to face England in a friendly at Wembley later this month.
The Football Association tweeted it will honour Astori at the game.
Matteo Renzi, a former mayor of Florence and now leader of the Democrat Party in Sunday's Italian election, tweeted: "This seems to me impossible. I don't believe it and I cry with the family and everyone at Fiorentina. Ciao capitano."
Dario Nardella, the current mayor of Florence, said the city would observe a day of mourning for the player's funeral.