San Francisco • The San Francisco 49ers sit alone atop the NFC West for now hardly the kind of firm hold on the division they owned last October.
Alex Smith threw a 12-yard touchdown pass to Delanie Walker late in the third quarter and San Francisco held off the Seattle Seahawks 13-6 on Thursday night as the 49ers won their long-awaited division opener.
Frank Gore ran for 131 yards and the 49ers (5-2) took over sole possession of first place in the NFC West by making just enough plays to win this defense-first game, featuring two teams allowing fewer than 16 points per game.
"That was the most physical 30 minutes of football in the second half that I have ever seen our football team play," 49ers coach Jim Harbaugh said. "It's a sweet win. It was a real football fight, and our guys won it."
Walker's score was San Francisco's first touchdown in seven quarters after an embarrassing 26-3 loss to the New York Giants on Sunday in a lopsided rematch of the NFC championship game. The tight end broke his jaw in two places at Seattle last Dec. 24 and sat out until the title game.
Smith went 14 of 23 for 140 yards in another subpar performance. The defense hung tough down the stretch.
NFC rushing leader Marshawn Lynch finished with 103 yards for Seattle (4-3).
It's now Harbaugh 3, Pete Carroll 0 since these two coaching rivals started facing off in the NFL last year after all those memorable moments in the college game.
Harbaugh's teams sure have shown they are quick to forget their losses. The 49ers improved to 5-0 after regular-season defeats since reigning NFL Coach of the Year Harbaugh took over before last season.
Pulling this one off could give the 49ers some momentum, too. It was the first of two straight prime time games for San Francisco, which doesn't play again until Oct. 29 at Arizona.
The defensive fight left the animated coaches shaking their heads and hollering on opposite sidelines all game, offering plenty of entertainment for the sellout crowd of 69,732 at balmy Candlestick Park.
"We found ourselves in a real slugfest here today," Carroll said. "I'm not surprised it could have gone that way with two good defenses and two teams committed to running the ball."
Smith's fifth interception of the season matched his total from all of 2011.