I say it's more of the pitching coaches fault than Dipoto.
How is it that every pitcher that comes to the Angels gets worse?
Then when Walden goes to Atlanta, he goes lights out? And Santana? And Chatwood? And even Kazmir becomes servicable?
And I'm not talking only about retreads. How is it Maronde, and Kohn can look so good in the minors, then turn into complete pumpkins when they get to the MLB level? Frieri comes from a different system, and looks unstoppable. But once in our system for a while, he looks utterly clueless?
When it happens once, sure it's possible. Twice, even possible. But after a while, when it happens over and over again, it can't be coincidence.