Everyone seems to have a theory about Aaron Hill, about how the second baseman has gone from being one of baseball's least productive hitters to a suddenly resurgent one since joining the Diamondbacks. There are those who point to him benefiting from a change in philosophy, going from a club in Toronto with a swing-from-your-heels reputation to one supposedly more suited to his approach. Some wonder about the role of luck, suggesting that Hill had more than his share of the bad kind. And still others say health was a factor, that more than once Hill hurried back from injury before he was healthy. A lot of baseball people like Hill as a player. They like his athleticism and his swing. They value his defense and appreciate the way he plays the game. And they seem to be trying to figure out how a player they consider to be so good could have struggled for so long.