SANTA CLARA, Calif. -- Barring an unexpected recovery by starting cornerback Tarell Brown, the San Francisco 49ers are preparing to start Tramaine Brock at cornerback.

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.