Health/durability is a lot less a matter of luck than most here care to believe. Some guys take better care of their bodies/nutrition. Others know how to subtly dodge the biggest hits. Some are very good at body control/balance and don't fall quite as hard. Others are just made of genetic steel. And the most durable have some combo of all of the above. Don't get me wrong, there is obviously some luck involved too. But not nearly close to all.
Best indicator, I would guess is past history, but then you still have the Frank Gores who bust up multiple times early, then become utter tanks later. Without having some regression analytics to lean this into, I'd suspect Frank would prove to be the rare exception to a general rule that past history is the best single indicator of injury proclivity. If true, that doesn't bode well for your man-crush turned turnip.