Here is my idea regarding player generation ,growth and regression model for career mode.
Each nation has player production quality ranging from 40 to 80.
Game will generate new players age ranging 16 to 20 at the end of the season and their potential ratings will be based on player production quality.
Each player starts with either 40% ,50% or 60% of their potential ratings
There are 3 types of progression , slow progression (players will reach their potential in 12 years) ,normal progression (8 years ) and fast progression (4 years )
Player regression is the process where players either get 25% ,35% or 45% reduction in their attributes over the years.
Player regression can be of 3 types , rapid decline i-e 3 years time ,(players attributes will reduce to the above mentioned % in 3 years time ) normal decline i-e 5 years time and slow decline i-e 7 years time.
Player regression randomly get starts b/w the age of 29-33.
When the player regress fully to its assigned % (25% ,35% or 45%) he will retire.
Feel free to ask any other questions.