I keep whoever I don't think will be picked. I know that's not the answer you're seeking but each world is different. However, for the most part, the 28 y/o who's a decent fill-in in an emergency will likely go untouched while the 22 y/o who still has pretty projections he won't reach will be snatched up like a hot dog at a fatty convention.
Coaching doesn't affect team performance. It only affect development.