Jason Heyward saw a doctor today, who explained that he has less cartilage between back discs than average person. He just needs to stretch.
Chipper has bad feet, and Jay-Hey has a bad back. Chronic pain is nothing new for many people, but it is especially troubling for someone as young as Heyward. Only time will tell how he reacts this year and in coming years to this obstacle.
My major concern from a selfish Braves fan's perspective is that Heyward can become very un-Heyward-esque when he has an injury, nagging or otherwise. Chronic injuries like this that flare up over and over can slow players down for periods of time without necessitating stays on the disabled list. That's the biggest thing I'm going to watching for with Heyward: reports about soreness that keeps him out of the lineup here and there.
Of course, while it may have kept him out of some games this spring, nothing has yes slowed him down at the plate; he's hitting .417/.517/.500.