Absolutely. With NBA Live 2000 you can actually add players to the draft pool before you begin a Franchise game.
Create a new player and change all his TEAM values to 39 (the Rookie team). Also change his ISGENERATE value to True. You can also assign various strengths, weaknesses and other generated rookie data (see the Players.dbf Guide for more info). If you start a new Franchise with the roster your new player will show up in the draft pool at the end of the first season.
It's best to fill in all the values. It isn't mandatory in recent lives but I seem to remember earlier dbf based Lives were particular about it. You might also want to change his ISCREATED attribute to False.