Alexander has over 1,200 yards on the ground for the third straight season.
Matt Hasselbeck was 19-of-31 passing for 233 yards and a touchdown. Bobby Engram caught six passes for 93 yards; and D.J. Hackett added six receptions for 67 yards and a touchdown, as the Seahawks (8-2) increased their winning streak to six games. Seattle defensive tackle Rocky Bernard picked up two sacks, giving him 7½ for the year.
Ken Dorsey completed 18-of-29 passes for 249 yards and a touchdown while Maurice Hicks gained 83 yards on 11 attempts. He scored one touchdown as San Francisco (2-8), which broke a 15-quarter drought without a touchdown, dropped its third straight contest.