The link is to an article by the sometimes maligned Phil Rogers of the Chicago Tribune. While Rogers gets off track sometimes, I think he's spot on with this analysis. The Royals received a great deal of potential from the Brewers. Greinke will most definitely exceed expectations in the National League (his 2009 season would've been top 5 all-time if he'd been in the NL, I'd wager). But Escobar and Cain should mature with good coaching (something I trust Yost with more than Hillman).
In addition, one should always weigh the value of a trade against what the trading team would receive if the free agent chose not to re-sign(two late first round sandwich picks, yes?). It looks like any of these 4 prospects meet or exceed the two-first-round-pick criteria. - TL