Alex Smith is trying to understand how he lost his job as starting quarterback of the San Francisco 49ers a month after being named the NFC’s offensive player of the week.

It’s not an easy thing for the NFL’s fifth-ranked quarterback to deal with this week, even though Smith already has experienced plenty of ups and downs in his tumultuous career since the 49ers made him the No. 1 overall selection of the 2005 draft.

Smith spoke with the media Thursday for the first time since coach Jim Harbaugh made Colin Kaepernick the team’s starting quarterback for Sunday’s game against the St. Louis Rams, a rematch of the last game in which Smith appeared.

Smith is now completely healthy from the concussion he suffered that day and medically cleared to play.

But he’ll be Kaepernick’s backup for the second consecutive week. Smith is uncertain what Harbaugh’s decision means for him the rest of this season.

“I feel like the only thing I did to lose my job was get a concussion,” Smith said.

Smith was playing some of the best football of his career when he was injured and left early in the second quarter of the 24-24 tie with the Rams.

He completed 7-of-8 passes with a passer rating of 143.8 against St. Louis, throwing for his 13th touchdown of the season on his final pass. The week before, Smith completed 18-of-19 for 232 yards and three touchdowns during a win over Arizona, setting an NFL record with a 94.7 completion percentage for a quarterback with a minimum of 15 attempts. He was named NFC Offensive Player of the Week for the first time two days later.

Smith ranks fifth in the NFL with a passer rating of 104.1 and leads the league with a 70.0 completion percentage.

Falcons beat Saints

The host Atlanta Falcons raced to a 17-0 lead and the defense made it stand up, picking off five of Drew Brees’ passes and ending his NFL-record touchdown streak with a 23-13 victory Thursday night.

The Falcons moved to the brink of clinching the NFC South and dealt a big blow to the Saints (5-7) and their fading playoff hopes. William Moore had two of the five interceptions, which were the most of Brees’ career and came four days after he had two passes picked off and returned for touchdowns in a loss to San Francisco.

Brees had thrown a touchdown pass in 54 consecutive games. He had an apparent scoring pass to Darren Sproles late in the first half, but it was nullified by a penalty.

Benson has surgery

Green Bay Packers running back Cedric Benson will remain on injured reserve for the rest of the season after having surgery Wednesday on his sprained left foot. The team’s most effective running back was able to resume practicing last week after being placed on the injured reserve but designated to return list Oct. 10, and could have played as early as Dec. 9. But he never did practice, and the odds of him returning seemed grim early in the week when coach Mike McCarthy said Benson was being re-evaluated.

Murray returns to practice

Dallas running back DeMarco Murray is finally practicing again.

It’s unknown if he’ll play Sunday night against Philadelphia, and whether his six-game absence is what ails the Cowboys’ running game.

Murray was a limited participant in practice Wednesday and Thursday in what coach Jason Garrett said was the most football work the second-year pro has done since spraining his right foot against Baltimore on Oct. 14.

Murray declined interviews after both practices, but did acknowledge a “good first day” in a playful exchange with reporters Wednesday.

“If he’s ready to go, it will be a boost,” quarterback Tony Romo said.

Murray had a franchise-record 253 yards in his first start as a rookie last season and averaged 5.5 yards per carry.

Titans get coaching help

Mike Munchak hired veteran coach Tom Moore to help the Tennessee Titans after firing offensive coordinator Chris Palmer, former coach of the Browns, and giving the job to Dowell Loggains.

Munchak said Thursday that the 32-year-old Loggains still will call the plays Sunday when the Titans (4-7) host Houston (10-1).

Around the league

Minnesota Vikings running back Adrian Peterson says he missed the team bus to Soldier Field on Sunday because he overslept. Peterson was about 20 minutes late to the stadium for the game against the Chicago Bears, then side-stepped questions after the game about the reason for it. … Oakland Raiders coach Dennis Allen says he told linebacker Rolando McClain not to come to practice a day after being held out for team-related issues. Allen would not address the reasons for his decision on Thursday other than to say there are “consequences to his actions.” McClain did not report to the team facility Thursday. …Tim Tebow was limited in practice again with two broken ribs, leaving the New York Jets backup quarterback’s status uncertain for the team’s game Sunday against the Arizona Cardinals. Coach Rex Ryan says that the Jets will continue to “monitor his situation.” … The Kansas City Chiefs claimed offensive lineman Hayworth Hicks off waivers. The 6-foot-3, 336-pound Hicks entered the league as an undrafted free agent with the Colts in April.