I think it's mental. He has the physical ability to be a top hitter. He's done it before. He's just lacking something. I think it's just that he can't be the #1 hitter. He needs someone else to lead.
I remember in Buck's day that in the first inning, you have to establish your fastball. And then add in your other pitches. Jim Clancy was a great example of that.
Remember the day he hit a homer and then sat the bench? The Managing Turd reported the best chance of winning the next game was without him. We got one hit that day. So Babe on the pine makes sense.