June 17 in the JS:

Three starts ago in Florida, Bush was struck on the pitching arm by a line drive in the first inning. He went on to pitch six innings and didn't miss a turn, and doesn't think that incident contributed to his slide.

"I suppose it's possible," he said. "I don't know. I can't put my finger on any one thing. We all have to make adjustments on the fly."

June 20 on McCalvy's blog:

Dave Bush revealed after the Brewers' 9-5 loss Detroit today that he's been dealing with some arm fatigue since that line drive off his elbow earlier this month in Florida. [...]

Had Parra not pitched himself down to the Minors, Macha said the Brewers would have probably used someone in Bush's place on Saturday. "These few days off could have done a little but [for Bush] like it did for Suppan," manager Ken Macha said. "But with four starters at this time, we're unable to do that."

I guess giving up thirteen runs in 6 1/3 innings helps a guy suddenly put two and two together.