NoMaas interviewed BA's John Manuel. I won't try to pass on all the juicy tidbits, so here's my favorite answer:
[Zack] McAllister was a second-round pick, hardly under the radar, but I see your point in that he hasn't put up the stats to make bloggers notice him. Same for [Ivan] Nova. All the answers to this are in BA's Prospect Handbook or in my Yankees chat from January. I had two scouts outside the organization and one in the system tell me Nova has shown three plus pitches at times. McAllister is a work in progress as the Yankees try to convert him from sinker-slider guy to using more of a four-seamer. They've experimented with him because that's what you do in player development--the goal is not to get outs at Staten Island, but in the Bronx. Optimally you'd have someone who does both but the Yankees are much, much more concerned with the latter.