Fiorentina captain and Italy worldwide Davide Astori died of a sudden illness at the age of 31 on Sunday, leaving Italian football in a state of shock.
The defender was found died in his hotel room in Udine on Sunday as the Viola prepare for their scheduled Serie A match with Udinese, which was later called off with all other Serie A fixtures.
Speaking to Sky Sports, the Chelsea boss said: "This is a tragedy, this news really hit at me".
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.
'It's very hard in this moment to find the right words for the family. It's very hard in this moment to speak about this tragedy.
'He was a fantastic guy, a great player but especially a fantastic guy. I stay close to his wife, parents and daughter.
Buffon wrote on Instagram: 'You have a young wife and family members who are suffering.
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Astori's body was taken to the Santa Maria della Misericordia Hospital for an autopsy.
After representing Italy Under-18s, Astori played 14 times at senior level.
In 2013, his lone goal was in a 2013 Confederations Cup third-place match against Uruguay.
The centre-back would go on to make 174 appearances in Sardinia, and earn his first Italy cap against Ukraine in 2011.
The Rossoneri said of their former player on their Twitter account: "A man who loved football and who grew up as footballer with us".
Fiorentina called on the media to respect Mr Astori's family in what it called a "terrible and delicate situation". #ACMilan are shocked by the passing of Davide #Astori.
Genoa and Cagliari players were visibly shaken and reportedly in tears upon learning the news during their warm-up for the now postponed early kick-off.
The Football Association tweeted it will honour Astori at the game. Prior to that he spent six years at Cagliari and one on loan at AS Roma. "Goodbye captain", said former Italian prime minister Matteo Renzi.
"It seems impossible. I'm in a state of disbelief and I cry with his family and all of Fiorentina".