too high decrease for each player in a team on the end of the season

[Perry Sih]

I think the OP is reffering to something else. If you do don't power train players ( use greens), players seem to get worse season after season instead increasing.

If the player does not gain 75 stat points before the end of the season, then indeed he will fall behind. Only players 21 or under could gain points this fast without getting power-trained.