I thought I'd throw out my opinion on this subject as we NEED Zack desperately. Here is a link to some video of Zack at the Royals home page. If it doesn't take you directly to video, click player select on the left hand side and pick Zack. It should list several videos to choose from. Watch some of Zack's video from 2009 and then again from recent 2010. Don't just watch one and call it good. Watch two or three of each year. What are the differences? You make the call. Perhaps we can determine what is wrong with Zack Greinke. My theory and mechanical analysis after the jump if you are interested.
Zack's non-throwing shoulder is showing us he is using more lateral rotation in his throwing than combining a linear and rotational force. What I mean is, his momentum is not going straight to the catcher's glove as it did last year. He is falling off the first base side or spinning. But it's not a huge difference, it's fairly small. But obviously enough.
It's something I've complained about before with our pitching coach. It's called Linear pitching. You generate all your force and momentum and expend it to the target. Not toward the first base dugout or on deck circle. From watching Greinke over the course of the season, he's lost a lot of what he did last year. The start to his windup is the same, a little twist at the top of the leg kick. However, from that point is where is becomes different. Last year, he drove that front arm/shoulder and left leg/hip directly toward Miguel or John. The result was stronger location and more movement. Especially on his slider. And especially when he threw downhill effectively. You can still throw just as hard without following linear principles, it's just from my experience you lose location, movement, and velocity when you "spin out".
Recently Zack questioned what was wrong with his slider. I believe this is part of your answer Zack, I hope you read RoyalsReview. The other thing that is probably wrong with his slider is that it's in his head. As a pitcher, if you feel one of your pitchers isn't working quite right, you'll spend more time on it as I'm sure Zack has done. You start to become obsessed with trying to find the answer. This is a good thing unless you start trying to make your pitches move. You have to trust the grip and the release. If you try to make the ball move more, it won't. You have to stay relaxed and trust that your body will be able to produce the result. When you try to make a slider move you end up with a pitch that moves more on one plane (across) rather than the two plane (across and down) slider Zack had last year. You also get frustrated. And tension comes from frustration. You will not perform at your highest level when you are tense.
I believe that if Zack gets back to driving into his target with the linear principle, he will be back to where he was last year. I hope this makes sense to some of you guys. If you have questions, ask. I'd love to hear other opinions on this as well.