A shot blocker leaves his man occasionally to get the weak side shot block? This is really news. You do know every good shot blocker does the same right? You think their shot blocks are only coming on the opposing center who their guarding or is it coming on guards or forwards who they leave their man for to block a shot?
^^^This^^^
To expand a little further. Every very good to great shot blocker gets burned from time to time throughout their careers. Often, it's because they left their man to defend against a guard or forward who beat their man off the dribble, only to have that player pass to the man they left for a dunk. Usually because weakside help didn't rotate fast enough or at all. It especially happens on teams like the Heat last year who were basically a group of guys who haven't played together much. It also happens with players like Whiteside, who are in the early stages of their development and are still learning that you can't block everything. When you have both at the same time, it ends up making the shot blocker look even worse.
Porous perimeter defense can make a center look bad as well. The Lakers with Hibbert are an example. Everyone expected that he would make the defense better by giving them a paint presence. Problem was, at least for the first part of the season, the Lakers perimeter defense was so bad that opposing guards and forwards were driving to the hoop at will. There have been times Hibbert has looked like a revolving door trying to spin and move in the paint to try to defend against what was coming at him.