Buster Posey hit .225 in the AFL last year too. The sample sizes are just way too small to take much from.
Boxberger certainly had terrible numbers out of the bullpen this season. But stuff wise, he just is on a different level than any other pitcher we have left who doesn't have major injury concerns (Looking at you Lotzkar and Thompson). But as a reliever he is a guy with a plus fastball (98 MPH is where he tops out) and an above average breaking ball. He had some control issues out of the bullpen, but they weren't there as a starter, so I figure that he will find his control and be alright.