Great question. My first reaction to that was that if he isn't in the 85 database, you are out of luck. That reaction is largely due to the fact that my rookies that enter these drafts, already had previous seasons where they aren't in the database.
That being said, I think perhaps this is an area we should explore. If a player is your current 85 roster, through baseball-reference, and had PREVIOUS WIS seasons...I think it would be a good idea to allow owners to enter these players into your roster. May help some of these last franchises to fill. If a player is on your current 85 roster, but is NOT in the WIS database for this season, AND does not have any previous WIS seasons...he would not be eligible.