O'Sullivan clinched the job with his performance in Thursday's 37-30 exhibition victory over Chicago, and coach Mike Nolan said it was time to make O'Sullivan's status official.

O'Sullivan, a long shot to become the starter when training camp began, overtook veteran holdovers Alex Smith and Shaun Hill during the past 2 weeks. The sixth-year player, now with his eighth NFL team, has never started a regular-season game.

Smith and Hill struggled to grasp new offensive coordinator Mike Martz' complex system, and O'Sullivan was given a chance in the lead role earlier this month. O'Sullivan worked in Martz' system last year when both were with Detroit.

"This hasn't been a case of Alex and Shaun not performing well," Nolan said. "This has been a case of J.T. performing very well. That's why we are where we are. J.T. has very good command of the offense, he's played well in all three preseason games, and now it's time for us to get ready for the regular season."

The 49ers invested $24 million in guaranteed money in Smith as part of a $49.5 million deal when they made him the No. 1 overall selection in the 2005 draft. They also signed Hill to a $6 million contract this year. O'Sullivan signed a 1-year deal for the veteran's minimum of $645,000.

Noteworthy

The trouble is "a loose ligament and [I'm] waiting to get more info on what I need to do," Merriman said in an e-mail to the North County Times.

He told the San Diego Union-Tribune that he tore the posterior cruciate ligament.

Merriman underwent surgery to repair cartilage damage 5 months ago, but has had persistent pain in the knee during training camp. He traveled this week to Birmingham, Ala., so the knee could be examined by Dr. James Andrews, who performed the operation.

* Houston receiver Harry Williams was taken off the Texas Stadium field on a stretcher after being hit in the head during a collision with a teammate. He was trying to make a tackle on a Dallas kickoff return. The initial report was that Williams had a neck injury, but the extent was not immediately known.

* Hall of Fame player and longtime NFL union head Gene Upshaw is being remembered this weekend with a moment of silence at NFL exhibition games.

Upshaw died Wednesday of pancreatic cancer at 63. His funeral is expected to be a private family service in California, with a memorial service to be held in Washington next month.

* Detroit signed quarterback Drew Henson after third-stringer Drew Stanton sprained the thumb on his throwing hand in practice Thursday. He will be out about a month.

Henson, 28, shared quarterback duty at Michigan with Tom Brady. He played three seasons as a third baseman in the New York Yankees organization before the NFL's Houston Texans drafted him in the sixth round in 2003. He was traded to Dallas in 2004, started one game and was released at the end of the 2006 preseason. He signed with Minnesota, which released him after training camp in 2007.

* Buffalo starting quarterback Trent Edwards won't play in tomorrow night's preseason game against Indianapolis because of a bruise above his right kneecap. Edwards missed his third straight practice since knocking knees in a collision with running back Marshawn Lynch on Tuesday. Backup J.P. Losman will get the start against the Colts. *