Some people are more injury prone than others, and some simply aren’t fast healers. It takes a special body type to have the physical ability, mental capacity, and durability to stick around the league. Clearly Luck was not healthy. You don’t miss an entire season if you are healthy. Luck had this mysterious ankle / calf injury that seemed to never heal. You can’t blame an athlete for being frustrated and unable to play at 100% physical capability. It’s like Jim Kelly in 1997. He could have played till 1999 or 2000, but why play as a shadow of his former self?