Right tackle Trent Brown is inactive for today's game, meaning undrafted rookie Erik Magnuson will start against the Seahawks and their sacks leader, Michael Bennett.
Brown injured his shoulder during a Thanksgiving day practice and missed Friday's session. He was listed as questionable for today's game.
Magnuson filled in at right tackle during a Week 8 game in Philadelphia, then started the following week against Arizona. Magnuson played tackle for Jim Harbaugh at the University of Michigan but mostly had been used as an interior lineman by the 49ers until recently. Another undrafted rookie, Darrell Williams Jr., will serve as the swing tackle today.
Bennett typically lines up at left defensive end for the Seahawks. His 6 1/2 sacks leads Seattle this year.
On defense, starting free safety Adrian Colbert (thumb) is inactive as expected. That means Antone Exum will start with Leon Hall backing him up. Exum will be the fourth different player to start at that position for San Francisco this season.
A pair of newcomers, Cassius Marsh and Sheldon Day, are active. Marsh will play at defensive end and Day will back up DeForest Buckner at defensive tackle. Two players returning from injury, Solomon Thomas and Tank Carradine, also will be in uniform.
Aaron Lynch, who is coming back from a Week 6 calf strain and who was not on the injury report this week, is inactive. He, Pita Taumoepenu, Leger Douzable and Victor Bolden Jr. are healthy scratches.
T Trent Brown
FS Adrian Colbert
DE Aaron Lynch
DE Pita Taumoepenu
NT D.J. Jones
DL Leger Douzable
WR Victor Bolden Jr.
DE Dion Jordan
S Kam Chancellor
CB Shaquill Griffin,
OT Oday Aboushi
RB Mike Davis
WR David Moore
LB D.J. Alexander