The 43-year-old, who was working as a goalkeeping coach at Pescara, directed the Serie B side's training on Friday morning before he fell at his home during the afternoon.
Emergency services were immediately called to his house, but it is believed that Mancini died before reaching the hospital.
He broke into Matera's first team in 1984 before enjoying spells at Foggia, Lazio and Napoli, among other clubs, during his 24-year career.
After retiring from football in 2008, Mancini became Foggia's goalkeeping coach in 2010, before following Zdenek Zemen to Pescara last summer.
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