Taking into account that players who reach the age of 30 already lose a percentage of their abilities, my suggestion is that when they turn 30 they do not reduce or increase their abilities, as suggested by this table.
Age
Injury prone / 30 / 31 / 32 / 33 / 34
Quite Easy / Equal ability / Low ability / Low ability / Low ability / Low ability
Easy / Equal ability / Equal ability / Low ability / Low ability / Low ability
Hard / Equal ability / Equal ability / Equal ability / Low ability / Low ability
Quite Hard / Equal ability / Equal ability / Equal ability / Equal ability / Low ability
As can be seen in the table, according to the Injury Proneness, the player will lower his skill level and upon reaching the age of 34, everyone will lower their skill level.
