Players get hurt. This does not mean that there is an inherent property that they possess called being 'injury prone'. Sometimes is just happens.
Guys who are legitimately injury prone are guys with chronic issues like Yao Ming, Quis (hopefully surgery helped), TJ Ford, or Brandon Roy or guys who play in such a way that they often get hurt like Gerald Wallace or Delonte West.
Wallace, for example, is not at all brittle. He just lays his body out so often that he is more likely to get hurt. It is possible that Rondo could end up that way due to his affinity for fully extending his body in the lane against mush heavier players.