What happened: San Francisco tight end George Kittle will play through a recent illness on Sunday. The 49ers additionally activated Mykel Williams and Upton Stout for the divisional contest.

Why it matters: Kittle's availability secures a primary offensive target for San Francisco. The additions of Williams and Stout reinforce the defensive front, arriving shortly after the team cleared practice squad space to accommodate the moves.

What to watch: Watch how the 49ers manage the snap counts for their returning players against Seattle.