OAKLAND, Calif. (AP) -- If the first preseason game is any indication, the Oakland Raiders can feel confident with any of their three top running backs.
The San Francisco 49ers can't feel the same about the three quarterbacks competing for the starting job.
J.T. O'Sullivan turned over the ball on his final two drives, and Alex Smith and Shaun Hill didn't perform much better as the 49ers committed four turnovers in an 18-6 loss to the Raiders on Friday night.
"We feel disgusted at the turnovers," said O'Sullivan, who threw one interception and lost a fumble. "I don't remember anything except for those two plays. Those things are 100 percent unacceptable. I am disgusted about those turnovers. You can't make excuses for something like that."
The Raiders ran for 248 yards, with the most notable performance coming from Michael Bush, who had a 5-yard touchdown run in his first game since breaking his leg in college more than 23 months ago.
After being injured in the season opener for Louisville in 2006, Bush missed the rest of that season and went from a possible first-round pick to a fourth-rounder. The rehabilitation then took longer than anticipated and Bush missed all of his rookie season, as well.
He is back on the field this year and ran for 27 yards and added 29 yards receiving in his first game.
"After the game I was halfway in tears because I had not been out there in so long, like two years," Bush said. "I was happy just to get the opportunity to play again. I was happy and at the same time a little bit nervous. I was all over the place."
With Fargas and McFadden ahead of him on the depth chart, Bush needs to show off his skills in short yardage and receiving to find a role on the team. He did just that, converting four of his five short-yardage attempts for first downs and going 23 yards on a screen from Andrew Walter.
"I'm very pleased with Michael," coach Lane Kiffin said. "He looked really good. I think we have something special with those three running backs."
Bush's touchdown came when he bulled his way through the middle on a fourth-and-1 play midway through the third quarter.
"To me that's a part of my game," said Bush, who ran for an NCAA-leading 23 touchdowns in 2005. "A running back should always be low. If you have to get that extra yardage, that's what you have to do."
Niners coach Mike Nolan picked O'Sullivan to start to get the chance to see his newest quarterback play after having already coached Smith and Hill.
O'Sullivan, who has never started a game in the NFL, struggled to move the ball on two drives against Oakland's starting defense. His third drive ended on an ill-advised throw downfield that was intercepted by Stanford Routt. O'Sullivan then fumbled while scrambling on the next drive. He finished 5-for-8 for 71 yards.
Smith was forced to compete for the starting job after a difficult 2007 season in which he struggled early, then injured his shoulder, and finally had a public blowout with Nolan. He threw incompletions on his first three attempts before leading the Niners to a 22-yard field goal by Joe Nedney at the end of the half. Smith finished 5-for-9 for 51 yards.
"We looked kind of indifferent," Smith said. "We all would like to take a look at this tomorrow. I made a couple of good plays. But I had a couple of opportunities out there, too."
Hill threw an interception on his first drive.
Oakland quarterback JaMarcus Russell also struggled in his first exhibition game after missing the entire preseason as a rookie in a contract dispute. Russell, who played in just four games as a rookie, was not sharp, finishing 2-for-5 for 15 yards in two drives.
Johnnie Lee Higgins, who averaged only 5.2 yards per punt return as a rookie last year, opened the scoring with a 53-yard punt return late in the first half for Oakland.
Frank Gore played only one series for the Niners, gaining 6 yards on two carries. ... Raiders kicker Sebastian Janikowski missed the game due to an injured left leg, and WR Ronald Curry sat out because of a sore hamstring. Oakland signed K Aaron Elling for the game. ... WRs Isaac Bruce, Bryant Johnson and Ashley Lelie missed the game for the Niners. ... Raiders rookie S Tyvon Branch broke his right thumb and will need surgery.