The wiry players seem to have less injury. I do think it's mostly a matter of flexibility; but it's also a matter of how they play the game as a result of their particular physical attributes. Some guys are so big and tough they just don't protect themselves because they believe that they can't get hurt. The more wiry guys are quite aware that they aren't a special physical specimen and so they automatically protect themselves in how they move and how they take a hit.
None of this is universal; but it does seem to be a significant generality.
