Over the last couple of years, we've seen the Diamondbacks have moves that essentially undervalue prospects in trade deals to teams that overvalue those very same prospects. When it comes to valuing prospects, the question becomes what makes one prospect more valued than another? My answer to the question is "Prospects are Lottery Tickets", where the value both balances upside and ability to contribute with the MLB club in the next 3 years.
On the Diamondbacks side, they seem to value the MLB side more than the upside value. In the 2015 calendar year, they've traded two first round picks and a former sandwich round pick in order to take care of MLB needs. Those players turned into Phil Gosselin and Shelby Miller. I'm not here to revisit past trades and what's done is done, there is no way to undo that deal. Instead we can only look at what we have now.
Perhaps the most valuable prospects from the Diamondbacks organization are Braden Shipley and Brandon Drury as the top pitching and position player prospect in the organization. Those players have better value because their odds of contributing on an MLB roster for the next 6 years are very high. Shipley is set to start the season either on a short stint in AA Mobile or outright start the year in AAA Reno. With Shipley only a phone call away from the majors, he's untouchable at this point. The same principle applies to Drury, who might end up taking the starting 3B job this Spring. Drury has already reached the majors and has looked decent in spurts while the overall numbers weren't good, but with the small sample size caveat and an unsustainable BABIP fueling those bad numbers.
When it comes to handling prospects, it's like playing the lottery. You try to keep the lottery tickets with the best chances of cashing out while getting rid of the ones that either don't pan out or have little chance of doing so in the future. Higher rated prospects have better odds of contributing to an MLB team in the future. If you're curious, I suggest you look up KATOH on Fangraphs' website.