I think there is a fear that Tebow will succeed in motivating his team to win; and if he wins with the Denver Broncos, other religious players will tell their agents to get them traded to Denver. Teams that don't do religious activities will add them in order to buy in to the winning tradition of Denver. After a while, we might even see crosses emblazoned on the back of their helmets, signifying that a Christian player is underneath that hard piece of plastic.
Eventually, football and baseball players will come to realize that their religious speeches and their demonstrative religious activities will win them better and better endorsement contracts. The shocking fall of a religious player, who goes from a goody-goody with clean, white shoes to a club-hopping meth-head with a thing for booty calling the wives of other players, will only enhance this sort of thing. It makes for millions of views on ESPN and Deadspin; alas, what could have been for player x if he hadn't used all of that codeine-laced Gatorade.
Religion in sports is a huge pain in the ass, by the way, if you're secular or some religion other than Christianity. But, when Christians win, it HAS to be because God favored them. That, in turn, drives people nuts.