Smiley, who has started every game on the 49ers' line for the last 2 1/2 seasons, is the second San Francisco lineman whose season ended in the last three days. Left tackle Jonas Jennings was placed on injured reserve Monday because of an ankle injury.

Smiley tore his labrum and dislocated his shoulder when Atlanta's Trey Lewis landed on him when Smiley dived to recover a fumble in the 49ers' sixth straight loss. Team doctors needed 20 minutes to put Smiley's arm back in its socket.

Smiley, a free agent after the season, decided to undergo surgery after a consultation with Dr. James Andrews in Birmingham, Ala., a team spokesman said last night. Smiley played 14 games with a torn labrum in his left shoulder last season, but his latest injury is much more severe.

David Baas, the 33rd overall pick in the 2005 draft, is expected to replace Smiley in the 49ers' starting lineup. The former Michigan center has played extensively as a backup, but couldn't beat out Smiley for the starting job in training camp.