SAN FRANCISCO — Alex Smith's most productive half of his career staked the 49ers to a 17-3 halftime lead Sunday against the Buffalo Bills.
Smith capped his 237-yard, first-half show with a 28-yard touchdown pass to Michael Crabtree. It came 24 seconds before halftime, and one snap after Patrick Willis forced a fumble that Dashon Goldson recovered.
Smith entered halftime with a perfect, 158.3 passer rating, completing 12-of-15 passes with two touchdowns, no interceptions and no sacks. He also had a 24-yard scramble that ranked as the half's longest run.
Smith's previous career-high for a half: 226 yards in the second half of a 2006 loss to the Eagles. His best for a first half: 195 yards in a Dec. 12, 2010 win against Seattle.
Smith is poised to break the 300-yard mark for only the third game of his career, and his first since Oct. 10, 2010 against the Philadelphia Eagles.
Kyle Williams' 43-yard touchdown reception put the 49ers ahead 10-3 in the second quarter, sparking an emotional celebration as Williams dropped to his knees and looked skyward. Williams lost his grandmother to breast cancer, and this weekend marked the start of the NFL's breast-cancer-awareness campaign.
It was Williams' third reception this season and only his fourth career touchdown.
The 49ers were poised to put up more points just before halftime, but Colin Kaepernick fumbled at the end of a 6-yard run. Kaepernick took a pitch from Alex Smith and fumbled after getting hit by linebacker Nick Barnett, giving the Bills the ball at their own 17.
Three snaps later, however, the 49ers forced a fumble, too, as Willis stripped Scott Chandler of a reception. Goldson recovered the turnover at the Bills' 28 with 29 seconds left in the first half.
The 49ers took a 3-0 lead on a 19-yard field goal, but only after Frank Gore failed to cross the goal line on second- and third-down carries from the 1. It was a situation perhaps better suited for Brandon Jacobs, a short-yardage specialist who's still waiting to make his season debut after an Aug. 18 knee injury.
After posting a 34-0 shutout last Sunday against the New York Jets, the 49ers nearly surrendered a quick touchdown, only to be saved by a holding penalty that nullified Leodis McKelvin's 80-yard punt return for a would-be score on the game's opening series.
The 49ers' five-quarter shutout streak ended early in the second quarter, when Rian Lindell's 31-yard field goal pulled the Bills even at 3-3 and capped a 75-yard drive.