Jennings, the starting right cornerback, left in the first quarter of the Seahawks' 23-20 victory.
It was not clear on which play he was injured.
The Seahawks were already missing starting defensive tackle Brandon Mebane, who sat out with a calf injury.
Punter Jon Ryan injured his ribs late in the game but coach Pete Carroll said he wasn't sure how serious it was.
Ryan was injured on Devin Hester's 89-yard punt return for a touchdown, when Chicago's Earl Bennett lowered his shoulder and leveled him with a block. Ryan stayed down for several minutes before walking off the field.
Information from The Associated Press contributed to this report.