Atalanta youth team player Andrea Rinaldi, who was on loan at Serie D side Legnano, died on Monday after suffering an aneurysm, the two clubs said.
"Andrea Rinaldi, our warrior, has left us," said Legnano's statement. "An aneurysm snatched him in the prime of life, with a life ahead of him and with a career that promised bright goals. A sudden and shocking tragedy, impossible even to imagine."
Legnano said 19-year-old Rinaldi, who had made 23 appearances since joining the club on loan in August, was taken ill on Friday. Italian media said he suffered a brain aneurysm and died in hospital.
Rinaldi joined Atalanta's youth academy at the age of 13 and made 35 appearances for the under-17 team, although he had yet to make his senior team debut. He also played for third tier Imolese and fourth tier Mezzolara on loan.