Well, he's usually isn't a good wide-open shooter. You have to get him in rhythm, whether he's guarded or not is pretty much irrelevant as far as I'm concerned with him. He's simply struggling behind the arc... can't pin point the problem myself, but I don't think it has much to do with getting open shots.
Even so, even with him struggling behind the arc, his FG% is at his career mark, so his devolution is a bit exaggerated.