I think its possible there's a huge confluence of bad luck that just happened to strike Heyward all at the same time, along with pitcher's adjusting to his swing and him not hitting the ball with the same authority. If you look at his batted ball percentages there isn't too much going on dramatically. His flyball percentages are up from last year but down from the previous 4 years with the Braves. The line drives (however broadly or vaguely defined) are where they are and as folks pointed out, he's been exceptionally unlucky on those. More importantly, his HR/FB% is 4.7%, which is one third his career rate. If that was normalized he'd probably still be having a disappointing offensive year, but it wouldn't be nearly as dramatic as it has been. But should he have more home runs? I don't know, I mean, completely anecdotally, I don't recall many long flyballs that Heyward has hit that have been caught on the warning track or whatever. But that is far from scientific, I'm sure there are more sophisticated measures of flyballs that I wouldn't know how to read anyway out there.