It's sort of funny that when he was drafted by the Giants, many teams were questioning his mechanics. He was viewed as an arm injury witing to happen. Now that he has a year an a half (or so) of MLB experience; he is viewed as "the Freak". FWIW I didn't read the SI article, but I heard that it actually goes as far as to praise his mechanics. It looks like a lot of his power comes from his long stride. His wind up is looks more lower body and less arm.