Penny went down in obvious pain after gaining 16 yards on a screen pass. He was initially ruled questionable to return before being downgraded to out.
"We don't know how serious it is, but it's significant," Seattle coach Pete Carroll said after the game.
Penny was starting to come on as of late and was pretty much in a split workload with Carson the past couple of weeks. But the tone around Penny's injury doesn't sound encouraging, which now opens the door for Carson to likely see a bigger workload going forward - and Prosise could be more involved as well.