SAN DIEGO –- Normally, I wouldn't be too concerned with an opening-day loss, but in Chicago's case, I'll make an exception for three reasons: Second-and-2, third-and-2, fourth-and-1.

Three fumbles against San Diego, like this one by Adrian Peterson, are a bad sign. (AP)

That succession of plays midway through the fourth period of the Bears' 14-3 loss to the Chargers on Sunday should bother the Bears and their fans, and here's why: Because they did nothing with them.

So what? So Chicago might not have the rushing attack it was supposed to have this season. Or that it had a year ago. All I know about a team without a running game is it puts more heat on the quarterback, and let's not get started on Rex Grossman.

For the moment, let's concentrate on what the Bears couldn't do, which is to push San Diego's defensive linemen aside when they had three shots at a first down. At the time, they trailed by 11 and were in decent position at the Chargers 36.

But that's where things unraveled. On second-and-2, Cedric Benson was jammed for no gain. On third-and-2, Adrian Peterson went to the same hole for a yard. On fourth-and-1, Benson went to the same spot again.

And with the same result: Zilch.

"It was pretty obvious what happened," losing coach Lovie Smith said. "They established the line of scrimmage, and we couldn't move them."

OK, OK, I get that. But it's the repercussions for the future that would worry me if I'm Lovie Smith. Remember, the Bears traded away running back Thomas Jones -– a guy who gained more than 1,200 yards in each of his past two seasons and ran for 112 yards in Super Bowl XLI –- to let Benson fly without a safety net.

Well, we're still waiting for liftoff.

After an 11-yard gain late in the first period, Benson never had a run for more than 4 yards. In those 15 carries, he did next to nothing -- producing 26 yards, one first down and one fumble. He had four carries for three yards each. Two for 2 yards apiece. One for 1 yard. Four for no gains. And one for minus-3.

In other words, Gale Sayers he wasn't.

So he was replaced by Peterson, who contributed another fumble -– this one leading to San Diego's clinching touchdown.

"We need to establish the run," Smith said. "You have to be able to do that or you can't throw the ball as you'd like."

Well, the Bears almost never throw the ball as they would like. Grossman was erratic again -- making one play here and one mistake there. But the poor guy was harried most of the afternoon, and when he made a big play, it was only when he and Bernard Berrian screwed up a deep pass intercepted by safety Marlon McCree.

Berrian, it seemed, quit on the ball. Grossman, it appeared, underthrew him.

"That was a miscommunication between Rex and Bernard," offensive coordinator Ron Turner said, "but put that one on me. We put that play in this week at practice, and I probably should've done a better job of calling something that we're confident in."

In essence, Grossman thought Berrian was cutting under the safety. Berrian thought he should be behind McCree. But that's not the concern. Grossman committed mistakes like that before, and the Bears recovered.

They recovered because their defense was rock solid and kept them in ballgames and because their running game was good enough to control the football. But not on this day, and the Bears better get that straightened out soon.

Because those three plays in the fourth quarter demonstrated this team might miss Jones more than it anticipated, and that Benson might not be the player the Bears envisioned when they made him the fourth pick of the 2005 draft.

I know, that's a rush to judgment, but good teams move the ball when they must. And Chicago did not. Sure, the Chargers have one of the league's top defenses, but three shots in the same hole? And for one yard?

You know what that tells me?

"Yeah," center Olin Kreutz said, "they kicked our ass and stopped us. It's unacceptable not to get the first down. We know we have to get better."

The Bears are confident they will, and what do you want them to say after one game? But even with the feeble Chiefs next on the schedule, they should be mildly concerned because without a rushing game, Grossman must be a quarterback he hasn't been.

He must be a quarterback who can win games.

I'm sorry, but that's not his job description. We saw what happened in Super Bowl XLI when he had to play from behind, and I'm not here to criticize Grossman for that lowlight. The guy was asked to do something he cannot, which is to carry this team.

He couldn't do it then, and he can't do it now. The Bears are the team to beat in the NFC North, but if they're serious about returning to the Super Bowl, they better find a running back and a running game soon.

If not, don't blame it on Rex.

"Our offense is a confident offense," wide receiver Mushin Muhammad said. "We believe in what we do, and when we do it well, there is no one better."

And when they don't? You just saw what happens.