Correlation does not prove causation and saying phrases like "I have no words" is not not a persuasive argument either.
I see Hinch and Fetter having an impact at the major league level. I don't see Harris having as much of an impact at that level, at least not yet. The Tigers would not be doing what they have done the last two years without the players, manager and pitching coach which Avila provided. Avila was terrible, but when you collect prospects for long enough (way too long in his case) you can build up a good base of talent.