I am going to have to call bullshit on BA's ranking on Iglesias ranking over the past 2 seasons:

Age Advancement
2010- Low A and AA at the age of 20
2011- AAA and cup of coffee at the age of 21!! Most prospects his age are in High A.
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Offensive Stats:
Last season in Double A he had .315 OBP and a .357 SLG which was accompanied by a .360 BABIP ( a most likely unsubstainable number). To go with this he also had BB% of 3.4 and a K% of 21%. This year in AAA his BABIP drops all the way to .279 (There is no batted ball data for the minors, but for any type of hitter  with above average speed this number is at least .20 points low) and a finishes the season with .285 OBP and .279 SLG. However his BB% increases to 5.4% and he cuts down on the K's to 15%.

Scouting:
When Jose was signed by the Sox the general consensus was that he had a special glove and relatively little bat.

After last season he was viewed as an 80 on the defensive scale and as a hitter with enough bat speed to possibly become a decent no power hitter for a short stop who needed to refine his approach.

In the 2011 campaign, Iglesias put up truly horrible offensive numbers, but never was there a general discussion in the scouting community that maybe the previous assessments on Jose's potential were incorrect ( if there is an actual industry source that can be cited saying this let me know) Yes, guys like Klaw and Sickels have said that they worry that he might not hit enough to be a starting ss for a contending team, but never have they challenged the previous assessment on his tools. Furthermore, though the results were ugly, a cursory glance at his walk and k rates seem to indicate that he has had some success in refining his approach.

So it looks as if BA has decided that the all glove relatively little bat short stop who in 2011was the 52 best prospect in all of milb, is no longer a top 10 guy in his own organization because he not so shockingly had a terrible year playing a league that his is 2 years too young for. Stats are a funny thing when being used to evaluate prospects and something that should be used sparingly. Unless there are scouts and other industry sources who are stating that they feel that his bat speed and contact skills that used to be rated highly have regressed, there is no reason for this type of astronomical devaluation.