The Fiorentina captain was found by his teammates in the morning after a reported heart attack.
“Ciao Grande Asto," wrote Milan defender Bonucci on Instagram.
“That's what I called you when we'd meet, for a game that saw us as opponents or for a Nazionale get-together.
“A smile, an embrace – one of the real ones – a person who was fair, honest and humble.
“How many time we laughed, joked and celebrated together. How many chats at the table sat side-by-side, or along the corridor that at Coverciano takes us to the (Italy training camp) bedrooms, on the pitch, or in the rooms.
“'Come on Leo, do a sweeping pass like only you know how' was what you kept repeating to me during tactical training sessions. With that smile that never ended and that made it clear how much goodness there was within you.
“You have gone to play football up there and you'll do it with the same big smile. The smile you always had."