This is one of my favorite approaches to evaluating pitchers, and this year one of the more disturbing. I think it relates somewhat to the discussion of the Rays' supposed glut of excellent starters, among other things.
According to the graph, the best starter on the staff in 2008 was Shields. No surprise there. But each of the other 3 who remain have some questions.
Kazmir remains in the southeast quadrant, but with a dramatically lowered GB rate. Both Garza and Sonnanstine are in the southwest and worst quadrant with below average K and GB rates.
There is nothing deterministic about the graph, of course. It does not account for low walk rates, something that improves Sonnanstine's chances of success. And in both Garza's and Sonnanstine's case, the numbers are close enough to average that with a small improvement they could move into a more promising quadrant. In fact, like Cliff Lee, they might even jump into the Northeast quadrant. I think that is especially true for Garza.
Nonetheless, it is a warning to us not to be smug. I see no reason to overreact, but at the same time it indicates to me that in some perspectives our starting staff is vulnerable.