A source told ESPN.com Sunday that Palmer is suffering from flu-like symptoms.
Palmer became ill sometime after the first session of two-a-days Saturday and didn't participate in the night practice or Sunday's session. Backups J.T. O'Sullivan and Jordan Palmer are taking all reps with the Bengals' offense.
Also, the Bengals signed veteran cornerback Jamar Fletcher, who played for Cincinnati last season and started two games. The signing comes one day after backup cornerback David Jones suffered a foot injury in Saturday's practice.
James Walker covers the AFC North for ESPN.com