In less than two months, Philadelphia Eagles head coach Chip Kelly might have gone from dunce to genius for signing Tim Tebow. The quarterback nobody wanted the last two years could be the very specialist the Eagles need to beat the NFL’s new extra-point rule. For the grand Kelly scheme to work, though, Tebow would have to be activated on game day not as the third quarterback—who can only be used if one of the first two go down—but as a special teams performer. Given Tebow’s size and reputation as a football player over a quarterback, that seems reasonable enough....