Ali'ifua (concussion) cleared waivers and reverted to injured reserve, according to the league's official transaction log.
Ali'ifua is now stuck on IR through the end of the league year unless he agrees to an injury settlement.
It's unclear exactly when Ali'ifua, who signed with the Seahawks at the beginning of August, suffered the concussion, but he will revert back to Seattle's injured reserve once he clears waivers.
After going unpicked in the 2017 NFL Draft, Ali'ifua signed briefly with the Chiefs but was waived before the season began. The 26-year-old is entering a deep but injured unit, so he's a long shot for a depth role and more suitable for the practice squad.