CHICAGO — J.T. O'Sullivan was already ahead of Alex Smith on points, but Thursday night's game seemed like the knockout blow.

It looks like J.T.O. by TKO.

Coach Mike Nolan again held back on an announcement by saying all three quarterback candidates looked good to him in a 37-30 victory over the Chicago Bears.

Nolan added that he needed to look at the film.

But the coach might as well fast forward to the 46-second clip of O'Sullivan's final drive of the night. It took two plays: A rainbow into the waiting palms of Vernon Davis for 40 yards and then a 37-yard laser in the end zone to Jason Hill.

And that, as they say, is that.

For the drive. For O'Sullivan's night. And, likely, for the quarterback debate.

He finished 7 of 8 for 126 yards with a touchdown and one interception.

His only incompletion was a shovel pass to Frank Gore that was dropped.

By one measure, it was perfection: O'Sullivan's 158.3 passer rating represented the maximum score.

Smith, by comparison, went 6 for 17 for 83 yards, one touchdown and a 71.4 passer rating. That was the technical merit, but he scored lower on artistic impression. Smith missed several throws to open receivers and on one pass led Josh Morgan into a potentially dangerous collision with free safety Mike Brown.

In all, the night served only to widen the gap between Smith (the former No. 1 pick) and O'Sullivan (the former Saint/Packer/Bear/Viking/Patriot/Panther/Lion).

The journeyman is approaching the summit of his journey: Sept. 7 against the Arizona Cardinals might be the first real start of his six-year NFL career.

But nothing is official - yet - even as the players grow increasingly antsy about a decision.

"I'm dying to know who it is," said the tight end Davis, who praised all three quarterbacks.

All three of O'Sullivan's drives resulted in points, enhancing his reputation for commanding the huddle. On the play before the touchdown pass, for example, O'Sullivan directed his comments to Hill.

"He told me, 'Get behind the safety. Get on your horse, get in the end zone and I'll get it to you,"' Hill said. "He got it to me." Smith, meanwhile, managed a 12-yard touchdown pass to Dominique Zeigler in the third quarter.

Because of O'Sullivan's quick night, Smith got some extra time with the first-string unit. He showed some flashes; he showed some flaws.

"The nice thing is, I know I'm capable of so much more in this system," Smith said, referring to offensive coordinator Mike Martz. "The frustrating thing is that there are a couple of plays you wish you could have back." Through three games, O'Sullivan is 20 for 33 for 351 yards, two touchdowns and two interceptions. Smith during that span is 16 of 38 for 196 yards with one touchdown and no interceptions.

There is one last preseason game left. Does Smith want one last shot to show what he can do? "That's up to those guys," Smith said. "My responsibility is to get better every day and continue to grow. I don't think that changes no matter what they decide." Together, the 49ers quarterbacks helped the offense roll out 425 yards - a second consecutive offensive showing against a tough defense.

Running back Frank Gore, who didn't play at all in the preseason a year ago, rushed eight times for 51 yards (a 6.4 average). The 49ers racked up 25 first downs to the Bears' 14 and would have won by an even larger margin if not for a 51-yard pass from Caleb Hanie to Brandon Rideau on the final play.

"We can dominate anybody if we go out there with the right game plan - which I'm pretty sure we'll have," Davis said.

But will you have an answer to the quarterback debate? "Coming soon," Davis said, "to a theater near you."