As i said, if you keep points or assign them to quality, they ll be counted the same way and your player will slow down proportionally, doesnt matter if you raise his q or mass points up. Everything not going into new role or sa slows down the growth rate. In the new season by losing his stat the player will re-fasten up, but dont forget he'll get a penalty by aging one year (from 18 to 19 is slight). Finally, even losing a star any player moving on a new age bracket will keep growing slower (>21yo, >23yo and so on).