On Baseball Prospectus Radio last week, Will asked A's beat writer Susan Slusser "what's wrong with Barry Zito?" Today, Phil Rogers asks the same question on ESPN.com.
In both cases, I'm rather flabbergasted neither Slusser or Rogers mentioned the most obvious reason: Barry Zito changed his delivery this year from the stretch. He decided to stand more upright instead of hunched over to take pressure off his knee.
The first question to ask when troubleshooting a problem is, "what changed?" So if you ask Ken Arneson the Barry Zito question, my first guess is this: the new delivery didn't work.
Why it didn't work, I'm not an expert enough to say. But I think whatever other excuses you make (missing Rick Peterson, thinking too much, less deceptive changeup, loss of control, etc.) are probably cascading problems from the original one of changing his motion.
If Zito misses Rick Peterson, it's probably because Peterson wouldn't let Zito change his motion, and Curt Young did.
I heard that he's gone back to the old style stretch delivery now, but I haven't seen it yet. I hope it will help get the old Zito back. I'll be watching tonight.