The move, which was expected, was announced by the team Friday.
Avril, suffered a neck/spinal injury while attempting to make a tackle in Seattle's Week 4 game against the Indianpolis Colts, and is still seeking medical opinions to assess the seriousness of the injury. "He's seeing a bunch of doctors, seriously looking at a big decision". The earliest Avril could return to the team is December 17 against the Rams.
Carroll told Dori Monson of KIRO Radio 97.3 FM during his weekly Friday appearance that Avril has been placed on the injured reserve.
Defensive coordinator Kris Richard is hopeful Avril will have a future with the Seahawks.
Avril is coming off a career year in 2016, recording 11.5 sacks and earning his first Pro Bowl appearance.
"Right now, we're unsure", Richard said on Thursday. It is very hard, but we have to keep moving on and we have to rely on the guys' active, yes next man in line. He would be eligible to return from IR after eight weeks and able to return to practice after six weeks.
With Avril eyeing an extended time away from the football field, more opportunities will likely come to backup Frank Clark. He has played in four games this season for Seattle, registering 1 sack.