While I would not have IBB'd Chavez, I can sort of understand the reason for it. If he hits a grounder, you have to get him at first base. He's fast, so any grounder that's mildly tricky could very well result in an infield single. Plus a guy with 2 AB's all season was coming up. That said, I think a tricky grounder with bases loaded could result in an infield single, too, especially since the runners would be going on contact. While I disagree with the decision, I can see the argument for it.