from Corey Pronman of The Athletic,
...extra value is given to players who have established themselves in the league and especially if they have proven themselves to be good players.
The pool of players considered are solely the top 10 players who are 23 and under as of Sept. 15, 2018. It’s an arbitrary cutoff, but I’m trying to get to the team’s core young talent and farm system. I don’t think most team’s depth players would change a lot, though, outside of systems which get a lot of value from having a ton of bubble prospects.