Impossible when stars drop every season. Grey skills drop too fast. Mostly you can see a lot of players with 1% of grey's and high % of whites. However your player could be like 5 stars but with high white skills and other player mixed of all type of skills but 7 stars but lower than 5 star player's white skills. It doesnt make sense.

If you not powertrain and especially when he is not super fast trainer, you should change these players after few seasons anyway.
And most of youth players anyway are slow trainers