MVP Baseball 2004 Hints for PlayStation 2
As soon as you get at least 5000 points and save your profile you can do this. Go into the place where you can unlock different players.
Unlock any player. Go into free agents and put that player on any team. Load your profile and you'll have 5000 points again.
Go back to the unlocking area. It won't say that you've unlocked any player, but that player will still be on that team where you put him.
Keep doing this until you've unlocked everyone. The game will still say that you've unlocked 0 players, but trust me, they are ALL there.
(Note: This will not work if you leave the player in free agents)