Gaines (ankle) has been ruled out for Sunday's Week 9 matchup versus the Seahawks, Bo Brack of GoPHNX.com reports.
Gaines continues to battle a knee injury and will miss his third straight game. Hayden Conner may make another start at right guard, though Isaiah Adams (ankle) -- who has been deemed questionable -- could take on that role if he's activated from IR on Saturday.