My concerns with Saunders are he looked like a sloth in the OF when he "was" supposedly healthy, not that he's an "injury risk" (what does that even mean).
Pillar has more upside offensively then downside IMO.
Bautista seems like he keeps himself in good shape, I think the injuries have been because of bad luck more than being "injury prone".
Pompey may well never become a good player.
It doesn't work that way though. You can really only gain muscle while eating at a caloric surplus, weight training, with sufficient protein intake, else you end up spinning your tires or losing muscle.