Smith to get the start Sunday for the 49ers

Alex Smith will start at quarterback Sunday when the San Francisco 49ers play host to the New Orleans Saints.

Smith is returning from a four-week absence because of a separated shoulder. He went through his second full day of practice Thursday, leading the first-teamers through workouts with no discomfort.

Smith hasn’t played since injuring his right shoulder on the third play of San Francisco’s 23-3 loss to Seattle on Sept. 30. San Francisco has lost four straight with an offense mired near the bottom of the league in most statistical categories.

Running back Frank Gore also expects to play Sunday despite a sprained ankle. Gore was limited in practice for the second straight day, mostly confining his workouts to individual drills.

An offensive lineman on the 49ers’ practice squad required medical attention after becoming dehydrated during a workout.

Paramedics treated Damane Duckett at the 49ers’ training complex after he cramped up during an afternoon workout, spokesman Aaron Salkin said. An ambulance and a fire truck responded to the complex, and medical personnel wheeled a stretcher through the front doors.

Defensive tackle Corey Simon retired from the NFL after trying to resume his career with the Tennessee Titans, saying practice and games started wearing on his body again.

Simon, 30, who was put on the non-football illness/injury list last season by Indianapolis, confirmed that he had dealt with polyarthritis in 2006. He signed with Tennessee on Aug. 28 and played in four of the Titans’ six games.

But recovering from each game and practice finally became too much for Simon.

“It’s just been a struggle, especially the last couple weeks, just getting my body to recover after every practice to go out there and do it,” he said. “I hurt every day. This is something I love to do, and I tried to push it as long as I could.”

The winless Miami Dolphins suffered another setback when linebacker Zach Thomas was ruled out of Sunday’s game in London against the New York Giants.

Thomas suffered whiplash in a car accident after Sunday’s defeat by the New England Patriots and will not even travel with his team.

Todd Bouman signed a one-year contract with the Jacksonville Jaguars, giving them a backup quarterback while David Garrard recovers from an ankle injury.

Bouman, 35, has played in 42 games with Minnesota, New Orleans and Green Bay.

New York Jets linebacker Jonathan Vilma missed practice for the second straight day because of a knee injury that could sideline him for Sunday’s game against Buffalo -- or longer. . . . New Orleans Saints starting center Jeff Faine could miss Sunday’s game at San Francisco because of a chest injury.

The Minnesota Vikings signed punter Chris Kluwe to a six-year deal, extending his contract through the 2013 season. . . . DeShawn Wynn remained Green Bay’s starting running back for the Packers’ game Monday night at Denver.