As a practical matter, the rules I mentioned in the previous post mean that a player who wants to play basketball and baseball has to be significantly better than anyone competing for the last scholarship slot in basketball for the coach to be willing to dedicate a "counter" slot to someone he can't control during the baseball season.
And that's before considering the significant seasonal overlap between the two sports.
That's one reason why the two-sport athletes who play either football or basketball plus baseball are usually studs. They have to be in order for both coaches to give them the opportunity.