ALAMEDA — Glen Coffee burst up the middle for 18 yards to end the first quarter. He sprinted around right end for 18 more to start the second quarter. He went 35 yards to the left side on his next carry in a stretch that he said reminded him of high school.

Instead, it came against the Oakland Raiders, which still had most of its starters in the game at the time. After spending much of the offseason trying to improve a leaky run defense, Oakland was exposed by the San Francisco 49ers on Saturday.

Now the Raiders have three weeks to get things right before LaDainian Tomlinson, Darren Sproles and the San Diego Chargers arrive for opening night.

“I don’t know if you are going to sell the farm and move, but there is definitely concern, definitely things we have to clean up,” linebacker Thomas Howard said. “I was disappointed with the run. Things need to change. Things must be cleaned up, definitely.”

Since going to the Super Bowl following the 2002 season, Oakland has had the worst run defense in the NFL, allowing 141.7 yards per game on the ground and 122 touchdowns rushing. The Raiders have allowed a 100-yard rusher in more than half of their games the past three years, with journeymen backs such as Ron Dayne, Maurice Morris and Kolby Smith reaching the mark.

After watching a third-round rookie, Coffee, gash them for 129 yards on 16 carries, and a sometime fullback in Michael Robinson add 97 more on 14 carries, it’s back to work for the Raiders. Oakland gave up 275 yards on 47 carries, with star Frank Gore providing only 7 on his two carries.

“I thought we had some guys not play very well,” coach Tom Cable said Sunday. “We have to do a better job adjusting to it as coaches, and then, two, I think you have to at some point set your jaw and decide you’re not going to get your rear end kicked like that.”

What was particularly galling for Oakland was the Niners kept hitting them with the same play, pulling offensive linemen around the end to create big holes. The Raiders were unable to make the needed adjustments during the game to solve those issues.

“We are just going to look at it, and I’m pretty sure the coach is going to come up with a solution to make sure that doesn’t happen again,” defensive end Greg Ellis said.

Ricky Brown did have seven tackles and an interception Saturday.

“We have a few things to shore up, but we have a good system in place,” Brown said. “Once everybody buys into it, the sky’s the limit for us, you’ll see.”