Palmer has made 26 consecutive starts. If he can't play this time, his younger brother, Jordan, would make his first NFL start.
Defensive end Antwan Odom (wrist) and safety Roy Williams (head) have been declared out. Williams didn't practice, and Odom was limited. Offensive tackle Dennis Roland (foot) is probable after practicing.
The uncertainty in Cincinnati's secondary also necessitated the team elevating rookie safety Jeromy Miles from the practice squad. He's the third new defensive back on the active roster this week. The Bengals signed Jonathan Wade and Fred Bennett and put Chris Crocker on season-ending injured reserve.
The Associated Press contributed to this report.