There was one at bat yesterday where it looked like his back was tweeked, he kept trying to stretch it. It looked like he was in pain, and the commentators mentioned it as well. If there are any issues, these are separate from his hamstring.
Kevin Barker on baseball central mentioned how much of a bad idea it was to play Bautista, who has had back issues in the past, at a position he isn't used to. For What? To Get Mastroini in the lineup? Or To get Reimold in the Lineup? Or Navarro.
If he is healthy he should be back at his position. He is the heart and soul of this team, you put him where he is best, and move everyone around him.