Atalanta midfielder Andrea Rinaldi died on Monday at age 19 after suffering a brain aneurysm at home three days ago.
Rinaldi was part of Atalanta's youth system and had been on loan at Serie D side Legnano this season.
Legnano, who confirmed Rinaldi's cause of death in a statement, called it "a sudden and shocking tragedy, even impossible to imagine."
Rinaldi joined Atalanta at age 13 and helped the club's Under-17s win the Scudetto and Supercoppa Italiana. He had been a key member of Legnano this season and scored one goal in 23 appearances. He would have turned 20 on June 23.
"President Antonio Percassi and the whole Atalanta family, deeply moved, send their most heartfelt sympathy to Andrea Rinaldi’s family members and A.C. Legnano for his passing," Atalanta said in a statement.
"Just as on the pitch you were always the last to surrender, this time too you fought with all your might not to fly away too soon. But that kind smile of yours will always remain alive in the heart of those who have had the good fortune to meet you."