This pattern of belief is an example of the logical fallacy, post hoc ergo propter hoc.
To be clear, I am not claiming, nor is it even necessary to prove, that Jesus is not helping Tim Tebow win football games. This is a logical fallacy even in the absence of contrary evidence. (As an aside, in no way do I believe Jesus helps anyone win football games.) The logical fallacy exists when a claim is made that because one event occurred after another, it's because of the preceding event that the subsequent event occurred. If there is no control, there is no way to prove causality one way or another, therefore a logical conclusion cannot be reached.
Tangent: When Tim Tebow is interviewed after the game and gushes about his lord and savior before answering a question, there's nothing a journalist can do about it. When journalists take non-stories that are examples of the same thing and put them on the front page, however, especially when there's no alternative plausible explanation offered, that's simply irresponsible. The irony here is that most people in the United States don't trust the media, but I somehow doubt it's these sorts of supernatural stories that sow the seeds of mistrust.
Of course you can't ignore the placebo effect. If believing that Jesus is helping him causes Tim Tebow to perform better, it doesn't matter whether Jesus (however you like to imagine him) is actually helping or not. And that's good enough for me. Because when the division standings are calculated at playoff time, Jesus-assisted wins count the same as non-Jesus-assisted wins. Go Broncos!