How is it that Ryan Theriot has a .347 OBP and is still pissing us off? Brendan Ryan's decision to have the same season he had in 2009 instead of the same season he had in 2010 is certainly part of it, but his newfound proclivity for making the kind (and frequency) of errors that had Pete Kozma stalled at Springfield probably isn't helping. UZR has Theriot at 3.3 error runs below average, which is already a career high worthy of Jose Bautista. When your fielding percentage is doing something interesting it's always bad news, which is why I should mention that his fielding percentage, at .951, is is 20 points below his career average.
And his evisceration of Lance Lynn—one of two by a defense that did its best to slowly acclimate Lynn to a Major League environment—won't even count as an error, because he got the one out.
If there were some reason to expect upside out of leaving Theriot at shortstop it would be worth doing. I don't think he's got a case of the yips, and I don't think he's suddenly become a -20 fielder at shortstop. But depending on the arrangement (I like the Allen Craig at Second experiment, and I'd like to see it continue) it's worth trying some different looks. If your star first baseman—the preeminent baseball player of his generation—is willing to move to third base on a managerial whim, your borderline-average shortstop should give some thought to denying his expressed discomfort about second base when he's playing this brutally at short.
As for the second ugly defensive play, I'm beginning to think Colby Rasmus's 2009 stint as an advanced-metric darling is as much a fluke as 2010; he's got great speed in the outfield, but most average center fielders do. (I think we were—not spoiled, exactly, but somethinged by watching Jim Edmonds teleport to the wall for seven years with below-average speed.) On the other hand, he tripled and hit a grand slam, and he can play center field. It's not a problem.