Tim Tebow, Cam Newton, Jordan Lynch, Colin Kaepernick . . . the list goes on and on.
It takes bad luck to get injured, not good luck to stay healthy. His season-ending injury (in a season in which he was in considerably lesser shape to what he's in now) was a fluke - hit at exactly the wrong time in exactly the wrong spot. Bad luck. Last season was not good luck. It was normal.