Renzo De Vecchi- Figlio di Dio

Precocious full back  Renzo De Vecchi  appeared for Milan as a 15 year old and played international football at 16. He remains Italy's youngest ever international, his debut coming (very unusually) as a half-time substitute in a friendly against Hungary on May 26th 1910. 
De Vecchi was a  small man (1.63m), but his status as a player was monumental. He was known by the Milan supporters as  Figlio di Dio  (The Son of God).
Football in Italy was amateur until 1926. De Vecchi however transferred from Milan to Genoa in 1913, a deal (instigated by Genoa's manager William Garbutt) that saw him pocket substantial relocation fees as he moved to take up a post as a bank clerk.
  De Vecchi became an idol at Genoa too, winning 3 national titles during a 16 year career that saw him make over 200 championship appearances. He later had 2 spells as Genoa's manager, guiding them into Serie A in 1935. 
Over the course of 15 years (interrupted by war) De Vecchi represented Italy 43 times, taking part in both the 1912 and 1924 Olympic Games.