John Abraham (concussion) to IR

TEMPE, Ariz. -- The Arizona Cardinals have placed outside linebacker John Abraham on season-ending injured reserve because of a concussion, the team announced Friday.

Abraham, 36, had been going through the final stages of the NFL's concussion protocol since Monday but had yet to pass. On Wednesday, coach Bruce Arians said Abraham failed the protocol Tuesday and needed to wait 48 hours before he could try it again. Abraham didn't practice Wednesday or Thursday, spending the open portion of Arizona's practice riding a stationary bike.

Abraham then failed the concussion protocol again Thursday.

"The concussion protocol really did its job in coming back and finding a couple problems," Arians said. "The doctors feel he should shut it down for at least a year, and we're glad that we caught it now and not later."

Arians said Abraham being placed on the IR/designated to return list was not an option because doctors would not let him play for at least a year.

Arians was hoping to have Abraham for Sunday's game against San Francisco. He would've re-entered the starting lineup once cleared to play.

"I felt bad because I think the concussion had part to do with the depression and everything that went on last week," Arians said. "And he was excited and ready to roll and hoping to get the OK from the doctor and then get that kind of news was real hard. We talked in the locker room this morning and you feel bad for somebody who's probably [at] the end of their line.

"We're going to miss his leadership. He was like an extra coach. He had so much knowledge, and he shared it with all the young guys every single day not just outside 'backers. Everybody. And was fun-loving, and I'll miss him in the locker room."

Abraham suffered a concussion in the third quarter of Week 1 on "Monday Night Football." A day later, he took a weeklong leave of absence. He decided to return to the Cardinals on Monday, saw a neurologist later that day and rejoined the team Tuesday.

During his Monday news conference, Arians said that Abraham was "ready to play."

"I knew a lot of it was to do with the headaches and the first real big one he's ever had," Arians said Monday. "There are other things we're dealing with, and he's fine with those."

On SiriusXM NFL Radio on Tuesday, Arians said he thought the five-time Pro Bowler was shaken by the concussion, his first such reported injury according to ESPN Stats & Information. The NFL's active sacks leader with 133.5, Abraham will earn his $3 million salary by going on injured reserve instead of retiring.