Lack of home runs does not necessarily mean he has lost power. From what I've seen (admittedly, I have not seen many games), Prince just isn't making solid contact as much as he did last year. He seems (and this is without looking at statistical evidence, so correct me if I'm wrong), to be hitting a lot of grounders and just not hitting the ball on the nose. EDIT: I wrote this before I saw rluz's graph about the grounders.