Giuseppe Meazza

Meazza's career as a player spanned 20 years (1927-47) and he won 53 international caps between 1930-39.
For Internazionale (Ambrosiana) Meazza scored 242 goals in 365 games. He was Capocannoniere on 3 occasions and scored 33 international goals in his 53 appearances, winning 2 World Cups.
Let's look at the early phase of Meazza's career:  

Season 1927-28:  2 goals on his first team debut age 17. 12 goals in 33 games. 
Season  1928-29:  Top scorer in the national championships with 38 goals in 29 matches.  This included 2 5 goal matches and 6 goals in 1 match (against Venezia). 
Season 1929-30:The first season of Serie A- Capocannoniere with 31 goals.

Not bad considering that Milan rejected him as a 14 year old for being undersized,
 and his first coach at Internazionale's youth side played him as a defender!