Forget about the Chicago defensive line. Here is what Vernon Davis and the 49ers really need to destroy Thursday night:

Their own stupid mistakes.

Shouldn't be surprised. But as we approach the 49ers' first prime-time game of the season, the NFL circus is out in full force, pointing and yelling and focusing attention on all the wrong stuff.

Yes, sentimentalists, this will indeed be Mike Singletary's first game as a head coach versus his old team. That would be meaningful if the Chicago Bears planned to aim their power running game directly toward the sideline where Singletary will be standing. The hunch here is, the Bears will instead run toward the goal line.

And we've got the never-ending 49er quarterback drama, with Alex Smith trying to show that his confidence is not melting down into a puddle of torment and dread.

Also, thanks to Davis, we now have the "Oath Of Destruction" sideshow. It sprouted up earlier this week when the 49er tight end opined that he didn't "see anything spectacular" about the Bears' front defensive seven. Davis also said: "I think we can destroy their front."

All right, whatever. It would be just as nice if Davis did not commit any false start penalties. And if 49er quarterback Alex Smith did not fumble the ball. And if the receivers all ran the proper patterns. And never dropped balls.

Because, see, this is what's killing the 49ers right now: The actual football nuts and bolts. The sideshows just obscure the true issues. If the 49ers are going to push their teetering season upright and back from the brink, they need to concentrate on the non-sideshows more diligently than ever.

Eric Heitmann, the 49er offensive center, explains it best. As he notes, four of the 49ers' five losses have come by one touchdown or less.

"In close games like that, one or two mistakes can make all the difference," Heitmann said. "We call them self-inflicted wounds - the offsides penalties, delay-of-game penalties. And they hurt you any time during a game, because you don't know what would have happened otherwise. ". . . We need to play with more of a mentally tough style in the second half of the season."

The 49ers are averaging 5.6 penalties per game so far. That's not a ridiculous number. But in their last three games, they've averaged 7.7 penalties, tied for third worst in the league. That number helps explain the monthlong losing streak as well as any other number.

And as Heitmann says, the damage from one little mistake early in the game is not always immediately obvious. Let's cite one example. Just by coincidence, it involves Davis.

Last Sunday, on the 49ers' first series of the second half, they lined up for a first down play at their own 35-yard line. Before the snap, Davis committed a false-start penalty that made it first-and-15 instead of first-and-10. This eventually turned into third-and-8 rather than third-and-3.

And so, on third down, guess what? Smith had to try a pass to Michael Crabtree. Incomplete. Fourth down. Punt. But without that first down penalty on Davis, maybe the third down is a successful four-yard run by Frank Gore. And maybe the drive keeps going. And maybe the 49ers score. And go on to win.

But at game's end, no one was thinking about that one penalty. They were talking about the other 49er blunders, including Smith's interceptions, the offensive line issues and assorted missed tackles by the defense.

All of that matters, obviously. But you get the feeling that if the 49ers stopped making the stupid minor mistakes, they could still make major strides and win eight or nine games. If not, they could easily lose nine or 10. And we'll start finding out Thursday night.

Davis, incidentally, was backtracking on his earlier remarks Wednesday. He explained that he wasn't "trying to stir anything up" and simply was trying to show confidence in his teammates.

It's doubtful the Bears took it the same way. In the NFL, if you invite people to pay attention to your mouth, they generally do. Takeo Spikes, the 49er linebacker who spent time in Cincinnati with the league's No. 1 circus act, Chad Ochocinco, was advising Davis about this.

"I told Vernon, 'The spotlight is going to be on you, so you better do what you're supposed to do every play,'"" Spikes said. "His response to me was, 'I do it every day.' And I said, 'Then we got your back."'

Singletary, meanwhile, was again revving up his sound bite machine. According to the coach, Thursday night's game will be exciting because "the country will have a chance to see the 49ers - the young 49ers - come of age in the second half of the season."

When pressed on what that meant, exactly, Singletary said: "You just have to watch the game. That's all I can tell you."

Good. We'll watch the game. And chart the mistakes. The little ones. Total destruction can work in the NFL. Remembering the snap count can be just as important.