As Dave Cameron noted, Jake Peavy isn't looking so good this season. None of his four starts have looked particularly pretty, and Net Runs confirms that, even granted Peavy's better looking 7.1 inning start in Cleveland, he's done a fairly poor job in all four starts.
The guy has been a walk machine (a bloated 13.6% of batters faced), and along with a lack of strikeouts (also 13.6%) and a 28.5% line drive rate as of today, it's clear Peavy's struggles aren't any product of bad luck, before you even delve into his velocity or pitch profile... which in turn offers plenty of evidence that something isn't right.
In the meantime, he's costing his team nearly 2 runs per start, and if he can't quickly adjust and resume getting guys out consistently, Peavy might need to look at a DL stint. The White Sox are struggling and need all the help they can get from a struggling pitching staff. Matt Thornton and John Danks can't do all the work ;P