Another week, another reminder of how tough it is to predict the NFL's concussion protocol.

Carolina Panthers linebacker A.J. Klein was on Friday ruled out of the team's weekend trip to Seattle. Klein, who played all 79 defensive snaps in Week 4 against the Bucs, was put in the protocol last week before the Panthers left for their bye.

Klein on Thursday said he wasn't sure if he suffered a concussion at Tampa Bay, or if he wasn't feeling well because of an illness he had before the game.

"I just wanted to be cautious, obviously if you don't feel right, you should tell [team doctors]," Klein said. "As a precaution, they put me in the protocol and I'll let the experts figure out what's going on."

Because he was cleared for non-contact drills and was at least limited in practice this week, it appeared Klein was on track to play against the Seahawks. But when he met with an independent neurologist Thursday afternoon, he was told he'd have to sit this one out.

"It may have just been sickness, but in these situations, especially after what's happened with Luke [Kuechly], they want to be cautious," Klein said. "It's a long season and they'd rather have a guy be healthy than to risk somebody's health putting somebody out there who's not ready."

Kuechly was finally cleared from the protocol this week after missing the past three games with a concussion. Coach Ron Rivera is adamant Kuechly won't play every snap in his return, and with his top backup Klein now out, Thomas Davis could continue to play a handful of snaps at middle linebacker. Rivera also left open the possibility four-phase special teams guy Ben Jacobs could help spell Kuechly if needed.

"I know Luke's going to go out there and just be an animal and tear it up," Jacobs said. "In my mind, I'm just there in case something happens."