Brown suffered a rib contusion Sunday in the 49ers' loss at New Orleans. He had to be taken off the field on a cart and he was in discomfort after the game. It is not impossible that Brown recovers in time to play Monday night at Washington, but a source close to the situation said the expectation is Brock will start this game and could perhaps start Dec. 1 at home against St. Louis.
Brock, a pending free agent, has been outstanding this season. He took over as the nickel cornerback in Week 3 when Nnamdi Asomugha was hurt. Asomugha could not reclaim the job and he was cut.
With Brock likely starting, seven-year veteran Eric Wright will be the No. 3 cornerback. He made his San Francisco debut at New Orleans as the dime and moved to the outside when Brown was hurt.
'You have to be versatile and ready for anything," Wright said Wednesday.
Meanwhile, Adam Snyder is expected to start at guard for the 49ers with Mike Iupati dealing with a sprained MCL in his left knee. Iupati was still on crutches Wednesday. He left the 49ers' sideline on a cart at New Orleans. He is expected to potentially miss a few games.
"Mike's a great player, a Pro Bowl player and helps the run game a lot," 49ers' running back Frank Gore said Wednesday. "But Snyder is a vet and it will be fine."