A couple weeks ago, the Eagles shocked the football world by announcing that their longtime offensive line coach, Juan Castillo, would assume the role of defensive coordinator. A pretty well regarded position coach on the offensive side of the ball, Castillo had been a linebacker in college more than thirty years earlier, and a defensive coach at the high school level in the 1980s. Evidently he always wanted to get back to his roots, and had worked closely with the late and legendary Eagles defensive coordinator Jim Johnson on game-planning. Still, the move has been widely questioned if not criticized; the Philadelphia Daily News headline, "WTF?" was fairly representative of the reaction.
I think the notion of non-transferable expertise must be more deeply rooted in sports and academia than other realms of human experience. The idea, I suppose, is that one spends his/her years burrowing ever more deeply into a specialized area of knowledge; this process commences upon receipt of some credential or position (an advanced degree, a coaching job) and continues unto retirement or death. Maybe the idea of transfer is somehow insulting to those who believe most deeply in this model. But while I grasp this idea in the academic sphere--a professor of economics isn't likely to effectuate a successful mid-career shift to astrophysics--it seems less certain in sports, and then in other areas it doesn't and shouldn't hold at all.
Right now I'm reading a book of Daniel Patrick Moynihan's letters, released last year. Over his career in public life, Moynihan was a domestic policy advisor to Presidents Kennedy, Johnson, and Nixon; a diplomat; and finally a Senator from New York. Each role was very different from the previous one, though I guess it's true that senatorial duties imply, or at least should imply, a broad expertise in both domestic and foreign policy. Meanwhile, George Shultz was Moynihan's colleague in the Nixon administration as Secretary of the Treasury, then served as Reagan's Secretary of State. Among his colleagues in that administration were James Baker and Don Regan--who famously switched jobs as Chief of Staff and Secretary of the Treasury in 1985.
These shifts seem to me of greater distance than Castillo's--in terms of subject mastery, I mean, not significance for humankind (though that too). For that matter, yesterday afternoon at work we saluted a colleague who's leaving the agency after nine years for a job in the private sector; during his tenure, he held senior roles in multiple departments each of which required deep subject knowledge. Yet he excelled in every one of those positions, in large part I think because his own skill sets--leadership, communication, empathy, the ability to think through and solve problems--were consistent.
I think when these sorts of moves founder, they do so because the person changing roles has a fault or faults that are totally distinct from the body of knowledge s/he must master in the new role. Mayor Bloomberg's appointment of Cathie Black to lead the schools might or might not prove such an example: he hired Ms. Black as a "superstar manager," which to my ear implies that she has many of the same characteristics as my former colleague mentioned above, but the article I've linked here casts some doubt on that characterization.
To bring things back 'round to Juan Castillo, his reputed strengths include motivation, communication and strategic thinking. If those strengths hold, it seems reasonable to assume that they'll transfer to his new role. There are limits on this, of course; I wouldn't want Castillo managing the Phillies, much as I wouldn't necessarily want a Moynihan or Shultz commanding the armed forces (though Trotsky managed okay during the Russian Civil War). But the notion that Castillo is doomed to fail seems silly given all the counter-examples of people who successfully managed similar transitions in other fields. What we mostly see here, perhaps, is that sports types take themselves surprisingly and excessively seriously in terms of how much these jobs demand.