49ers to start Troy Smith vs. Rams

San Francisco 49ers coach Mike Singletary announced Friday that Troy Smith will start at quarterback Sunday against the St. Louis Rams.

Troy Smith, who led the 49ers to their second win of the season in his third career start in Week 8, took most of the snaps with the first team at practice Friday. Alex Smith is recovering from a left shoulder injury. The former No. 1 overall pick has been ruled out for Sunday.

Alex Smith injured his shoulder on Oct. 24 in a 23-20 loss to Carolina and spent time in a London hospital before the 49ers beat the Broncos 24-16 in the NFL's annual game across the pond.

Cornerback Nate Clements (ankle) and guard Chilo Rachal (personal) are probable.