CHICAGO — J.T. O'Sullivan made a perfect case to start. And Alex Smith's counter-argument didn't measure up.

Even so, 49ers coach Mike Nolan wasn't ready to announce a starting quarterback.

O'Sullivan threw for 126 yards and a touchdown in his limited time while Smith struggled, and the San Francisco 49ers beat the Chicago Bears, 37-30, last night.

Although the third preseason game usually is a dress rehearsal for the opener, Nolan wouldn't declare a winner in the quarterback race.

"We will talk about it more (today)," Nolan said. "I would like to watch the film, talk to our players, before any announcement or anything like that is made. But I did like what I saw in all three of them."

After two mediocre outings against Oakland and Green Bay, O'Sullivan couldn't have performed any better against the Bears.

He was 7 for 8 with a perfect 158.3 passer rating in his third preseason start. He led the 49ers (2-1 preseason) to field goals on the first two possessions and a two-play, 77-yard touchdown drive on the third one. He hit Vernon Davis with a 40-yard pass and then scrambled to his right before throwing a 37-yard touchdown pass to Jason Hill to give the Niners a 13-10 lead less than a minute into the second quarter.

"That was a great play call," he said. "Jason did a great job of running so fast across the field and just made a great play on the ball."

And O'Sullivan did a good job, too. The question is whether he did enough to beat Smith, who came on early in the second quarter and was 6 for 17 with 83 yards and a touchdown, even though Nolan wasn't about to make an announcement. He even left the door open for Shaun Hill, who played well late in the game.

He entered the game after Chicago's Garrett Wolfe fumbled the kickoff following Hill's touchdown pass, giving the Niners possession on the Bears' 16. Moran Norris ran it in from the 1 to make it 20-10.

Smith also led the Niners on a 62-yard drive that ended with a 12-yard touchdown pass to Dominique Zeigler, giving the 49ers a 27-20 lead with 9:28 left in the third quarter. Otherwise, it was a rough night for him.

Hill replaced him late in the third quarter and was 6 for 7 with 60 yards against the Bears' reserves. But after yesterday's game, the starting job appears to be O'Sullivan's even though there was no announcement.

"Everybody wants to know who the starting quarterback will be," Davis said. "I don't know. I have no idea. Everybody looks good to me."

The Bears' quarterback drama ended Monday when coach Lovie Smith selected Kyle Orton the starter over Rex Grossman. And Orton backed it up with a strong showing.

He was 10 for 17 with 147 yards, two touchdowns and no interceptions for Chicago (0-3). He had four passes of 18 yards or more, including a 55-yarder to Mark Bradley — a big improvement over the first two preseason games, when his longest completion was 17 yards.

RAMS

RB JACKSON SIGNS

Steven Jackson signed a six-year, $44 million contract, ended a 27-day holdout, and was on the field for practice with the St. Louis Rams yesterday.

And all was forgiven.

Coach Scott Linehan, who conducted a month of practices without the centerpiece of the offense, joked that he gave Jackson "a big hug" and then asked for a loan. Offensive tackle Orlando Pace, no stranger to holdouts, said he was happy "big time, big time" to see the bruising runner.

The 235-pound running back had been entering the final season of a five-year, $7 million deal he signed as a first-round pick in 2004.

Linehan said he understood the business end of the game after Jackson got a deal that includes more than $20 million in bonuses and puts him third on the salary scale on the team, trailing only quarterback Marc Bulger and Pace and fifth among NFL running backs.

NOTES

Texans: Fullback Jameel Cook was arrested and charged with marijuana possession Wednesday. A Fort Bend County sheriff's deputy stopped Cook at about 7:30 p.m. because his 2007 Mercedes sedan had no front license plate or registration sticker, sheriff's department spokeswoman Terriann Carlson said yesterday. He's free on a $500 bond.

Steelers: Pittsburgh signed linebacker James Farrior to a five-year, $18.2 million contract with a $5 million signing bonus yesterday. He'll make $12.6 million over the first three seasons. The last two years of the deal are meant to lessen the salary cap impact of the deal.

Dolphins: Miami running back Ronnie Brown will likely miss tomorrow's exhibition against the Kansas City Chiefs with a strained right thumb. Dolphins coach Tony Sparano said yesterday that Brown is not expected to play.

Bills: Buffalo bolstered its offensive line by signing undrafted rookie free agent Dustin Dickinson. Dickinson spent two months with Seattle before being released in late June. He played college at Houston, where he appeared in 49 games, including 39 starts.