I'm actually a huge supporter of sending guys down to the D-League so they can get playing time and hopefully develop their game in a competitive setting.
With that said, I think there are two different types of development.
1.) Professional Development
By this I mean, is the player a professional.
Is the player mature enough to put in the extra time, eat right, live right, and conduct each day to maximize his chances of being a success in the league.
2.) Skill Development
This is the development of the actual basketball skills. Learning how to play in a system, getting better with the off-hand, getting more consistent with the shot, ect.
For players who have a well developed professional demeanor, who can be counted on to do the right thing in order to advance their careers, I think sending them to the D-League is a great move. They'd be able to understand that the move is to give them an opportunity to develop their basketball skills against other hungry basketball players.
For players who have not developed a professional demeanor, I think sending them to the D-League is a very bad idea. I'd much rather that player spend time with the team, practice against the team, and hopefully be in a position to be accountable for their actions by the watchful eye of the organization and perhaps fellow teammates.
I think that Whiteside wants to be a great NBA player. But he has had his struggles, and so for him, in this instance, I truly believe he would be much better served staying with the Kings. Hopefully, Westphal can find him 10-15 minutes in the rotation, and he can grow and develop into his potential.