Born in Milan, Renzo De Vecchi is the youngest player to play in a Serie A game for A.C. Milan, making his debut at 15 years and 284 days, on 14 November 1909, in a 2–1 home win over Ausonia. He soon becoming a member of the starting line-up on the left side of the back-line, although he was also capable of playing in the centre or even in midfield. Due to his class and playing ability, he was given the nickname "Il Figlio di Dio" ("The Son of God") by the Milan fans. He later moved to Genoa in 1913, winning three Italian League titles during his time with the club, before retiring in 1929. Between 1927 and 1929, he worked as a player-manager for Genoa, and during the 1929–30 season, after retiring as a player, he became the club's manager for a season, temporarily moving to Rapallo in 1930, for three seasons. He returned to Genoa in 1933, and he helped the club to gain Serie A promotion, winning the 1934–35 Serie B title, before retiring, after which he pursued a coaching career.