Tomlin mentioned in the post game presser that they didn't want to leave "any bullets in the gun". They knew they needed to get a fast start and not just into a 3 and out situation. Now was not the time to sit back and "do what we do".
This also, along with the short passing game that we're talking about is just what the Steelers offense needed. Nobody on the Titans saw that coming at all. Finnegan took off running down the field as soon as the ball was snapped and never even saw Mundy catch the ball. Wasn't the prettiest pass by Sepulveda but as long as it got there, that's all that counts, LOL. This is the kind of ingenuity and unpredictable nature that you have to have. I hope we see it more often but I'm not holding my breath.
All in all, it was a key play in the entire game. If they just punt it away the offense walks off the field after another missed opportunity and who knows what would have happened. Not that I'm foolish enough to say that the Steelers would have lost had they not run the fake punt, but I think it gave them a momentum boost early and kept the Titans on their heels.