With its .500 record, the Seattle Seahawks remain in the hunt for the NFC West title and a playoff berth.
Seattle travels to San Francisco on Sunday for a key divisional matchup with the fading 49ers.
The Seahawks (6-6) rallied from a 14-point deficit last week to post a 31-14 victory over the Carolina Panthers. The victory kept Seattle in a first-place tie with the St. Louis Rams and on track for a possible fifth divisional title in the last seven seasons.
Marshawn Lynch ran for a career-high three touchdowns last week and might need to take on a bigger role if receivers Mike Williams and Ben Obomanu are not able to play. Williams, already nursing a left foot injury, left the Carolina game after spraining his left ankle on Seattle's first offensive possession. Obomanu suffered a laceration that required stitches.
In his only game career game against San Francisco, Lynch ran for 134 yards and averaged 8.4 yards per carry as a member of the Buffalo Bills in 2008.
First-year Seattle coach Pete Carroll, who was born in San Francisco, is looking for a season sweep of the 49ers. In his first game as Seahawks coach, Seattle scored 31 unanswered points in a 31-6 home win over San Francisco.
Matt Hasselbeck threw a pair of TD passes in the season opener and has completed 226 of 381 passes for 2,621 yards and 10 TDs to go along with 11 interceptions. Hasselbeck threw for 229 yards last week against the Panthers and has won 10 of 14 career starts against San Francisco.
Hasselbeck has thrown 25 touchdown passes against San Francisco - more than against any other team in the NFL.
The 49ers (4-8) will have Alex Smith back at quarterback after a five-game absence. Smith hasn't played since separating his left shoulder in a 23-20 loss at Carolina on Oct. 24.
The No. 1 overall draft pick in 2005 has completed 143 of 242 passes for 1,554 yards, nine touchdowns and interceptions. Smith, who has a career record of 17-30 as a starter, is a free agent after this season and is unlikely to return.
Former Heisman Trophy winner Troy Smith went 3-2 as the starting quarterback for the 49ers, throwing for 1,023 yards, four TDs and three interceptions.
San Francisco is coming off a 34-16 loss at Green Bay, its first game since losing Frank Gore to a fractured right hip that ended the season for the 49ers' leading rusher. San Francisco finished with 97 yards rushing on 22 attempts, but tight end Vernon Davis had four catches for a career-high 126 yards and a touchdown.
Gore, a two-time Pro Bowler in his sixth season, ran for 853 yards and three touchdowns this season and also caught a team-leading 46 passes for 452 yards and two TDs.
The 49ers have not allowed a 100-yard rusher in 18 consecutive games, the second-longest active streak in the NFL.