I like Greene as a prospect as well, but I think doug's criticisms are very fair. When evaluating players as major league prospects, age will always be a factor. Greene may eventually make it to the bigs as a valuable starter/utility guy, but his age and level he played at last year tend to indicate he won't be a future star player. Generally, if a guy is starting the season in the minors at age 26, he's no longer looked upon as an impact big leaguer. As someone who'll turn 25 in September, Greene would have to rise quickly to still look like much of a prospect.
Yorman Rodriguez is a perfect example of this. He's currently Redszones' 7th rated prospect, and that is based largely on age and tools. The older he gets, the more he has to produce to still be considered a top prospect. Once you hit a certain age, if you aren't putting up big numbers in the high minors, you're easily forgotten about in favor of younger guys whose future is still completely unknown.
Brodie Greene could put up comparable (or even better) numbers to last year and finish the year in AAA and I'm sure doug and many other people would probably reevaluate his position on their prospect list at that point