SAN FRANCISCO -- About the only thing new for Alex Smith in his return to Candlestick Park was the coach on the sideline.
Considering the offense's performance last week, that was a major improvement.
Smith threw for 126 yards and an interception in coach Jim Harbaugh's home debut, getting showered with a mix of boos and cheers in the San Francisco 49ers' 17-3 preseason victory over the cross-bay rival Oakland Raiders on Saturday night.
"We improved from last week. But if we want to be the team we're talking about being, we have to finish in the red zone and can't turn the ball over," Smith said. "In my thinking, those first few drives, we didn't finish and then had the pick. Can't do that."
While the running game racked up huge chunks of yards, the passing game wasn't always crisp.
Smith was 8 for 13 and came up empty in the end zone. He had a pass intercepted by defensive end Matt Shaughnessy in the second quarter and led the 49ers to a field goal in one half of play.
The 2005 No. 1 overall pick at least left healthy. Oakland starting quarterback Jason Campbell didn't return after taking a couple of blows on a scramble play in the second quarter. He was scheduled to have test for a concussion.
Bay Area fans might have left with more questions than answers about the two starting quarterbacks.
Although San Francisco's offense was a complete turnaround after a 24-3 loss in the exhibition opener at New Orleans last week, Smith's performance mimicked so many others from his previous six seasons: He anchored three long drives, showed signs of progress and made one major mistake.
With second-round pick Colin Kaepernick waiting on the sidelines, the pressure is on Smith to finally perform. Kaepernick threw for 52 yards on 6-for-8 passing and -- like Smith -- benefited in long drives by a strong running game led by Kendall Hunter, who finished with 105 yards and a touchdown on nine carries.
"There's a lot to learn, new terminology and stuff like that," Hunter said. "With new coaches, you just got to adjust and learn everybody and get used to everybody."
The Niners opened with a 16-play, 79-yard drive that stalled 2 yards short of the goal line. The ensuing field goal attempt was botched because holder Andy Lee couldn't corral the snap, throwing the ball away and injuring his hip getting pounded to the ground by defenders.
On the second drive, Smith tried to squeeze a pass to tight end Vernon Davis on the left sideline, Shaughnessy dropped into coverage and was gift-wrapped an interception. Smith walked off the field to a slight chorus of boos, the only cheers coming from Raiders fans.
Smith, the presumed regular-season starter, said he never saw Shaugnessy drop into coverage. Both Smith and Harbaugh believe it was an error in recognizing coverage and not a reminder of past mistakes.
"We talked about (the interception)," Harbaugh said. "We feel that's a correctable thing. I know why it happened. We just have to do a little better job of our eyes."
The best highlight of the night for the 49ers came when new receiver Braylon Edwards made a one-handed catch on the sideline for 32 yards on final drive for the first-team offense. San Francisco settled for a 23-yard field goal by David Akers, who also had one punt blocked filling in for Lee.
Not that the news was any better on the other sideline.
The Raiders already were without several key players because of injuries, notably receivers Jacoby Ford and Louis Murphy and running back Darren McFadden. Now they could be adding another to the list.
Campbell was hurt late in the second quarter when he scrambled to his left, was tackled by Justin Smith and appeared to take a knee to the helmet from linebacker Ahmad Brooks. Campbell was down on the ground briefly while being checked out by trainers.
"The ball got knocked out of my hands. I tried to go dive on it and caught a knee to the head," Campbell said. "
He sat on the bench after being replaced by Trent Edwards, finishing with 74 yards passing. Sebastian Janikowski made a 46-yard field goal in the fourth quarter for Oakland's only score.
Raiders coach Hue Jackson, still searching for his first win at the helm of the silver and black, didn't blame the injuries for the poor performance.
"That has nothing to do with tonight," Jackson said. "Tonight we didn't play Raider football. We didn't play like a Raider. That's just the truth. Let's call it like it is."
Hunter had a 52-yard TD rush in the third quarter and Xavier Omon ran for another from 5 yards out in the fourth quarter.
After losing 24-18 to the Arizona Cardinals in its preseason opener, Oakland didn't exactly make any strides the second time out. The Raiders, who have struggled to find the end zone once they're close, have only scored one touchdown in eight trips inside the 30 this preseason.
"I think we are still knocking some rust off," defensive tackle Richard Seymour said. "It is good to get out here and work with our teammates, but we still have a lot of work to do."
Raiders TE Kevin Boss had a left knee injury. ... Lee was scheduled to undergo test on his hip. Harbaugh said he didn't think the injury was serious.