I think it is a combination of the league figuring him out and he hasn't figured out that he's been figured out yet. Clear as mud I know. I think he's dealing with a nagging shoulder injury as well. The combination of the two = down year. Sort of reminds me of Francoeur.
Beyond that I don't know. If the player isn't on my fantasy team or on the Yankees I don't keep up with him much during the season, and I traded the rights to Heyward during the off-season so he's been off my radar.
"You stay bought into it when you see your opponent sucking air and physically failing, and you're still fit and ready, and you know you own his ass."
-Former Bama LB Cory Reamer on Coach Cochran's training program