Has the Raiders' QB carousel stopped? Gradkowski goes on IR

Only one day after Bruce Gradkowski acknowledged that he didn't need surgery on his injured shoulder, the Oakland Raiders officially placed him on injured reserve and signed former San Francisco 49ers quarterback J.T. O'Sullivan. And one week after being replaced, Jason Campbell finds himself the starter again.

Before the Raiders announced either move -- via Twitter -- O'Sullivan was seen stretching and warming up at the start of Thursday's practice. Gradkowski attended the team's morning walkthrough, but he was nowhere to be seen at the start of practice, Comcast SportsNet Bay Area reported.

"It would be a week, two weeks, something like that before he could even throw again or practice," Raiders coach Tom Cable said of Gradkowski. "As you look at what's left on our schedule, it's just not enough time. A good decision was made to move forward."

The Raiders gave no indication that Campbell wouldn't start last Sunday, but Cable instead went with Gradkowski against the Miami Dolphins. Gradkowski threw two interceptions and had a 62.5 passer rating before taking a hit on his throwing shoulder late in the fourth quarter.

Cable initially expressed concern that the quarterback's injury could be season-ending, but an MRI confirmed that Gradkowski has a third-degree shoulder separation, the same injury he sustained earlier in the year. It doesn't require surgery.

"It seems like my shoulder's still strong to where if I just let it heal right, I'll be all right," Gradkowski said Wednesday. "I don't see the season being over for me yet. I'm just going to keep preparing, keep rehabbing. I'm thinking a couple of weeks and get back."

Campbell handled the majority of reps in practice Wednesday, and Kyle Boller was the backup. Gradkowski attended practice and even donned a helmet at one point, but he was held out of all drills.

O'Sullivan, who was drafted by the New Orleans Saints in 2002, also has spent time with the Green Bay Packers, Minnesota Vikings, New England Patriots, Carolina Panthers, Detroit Lions, 49ers, Cincinnati Bengals and San Diego Chargers. He appeared in games for four of those teams -- the Packers, Lions, 49ers and Bengals.

Notes: LB Rolando McClain (sore foot) and DT Richard Seymour (rest) didn't practice Thursday. ... WR Chaz Schilens (foot), CB Nnamdi Asomugha (ankle) and S Tyvon Branch (shoulder) were limited.

The Associated Press contributed to this report.