Despite the rough start, Tim Tebow's NFL audition at this week's Senior Bowl proceedings hasn't been a total disaster — Thursday's practice, in fact, was pretty clearly his best after four days in Mobile. With an army of skeptics already out in force, though, he couldn't afford to just keep his feet; he needed a knockout that hasn't come. Given their biases coming into the week, no matter what kind of counterpunch Tebow throws from this point, the first impression se…