After promising rookie running backs Joe Williams and Matt Breida played a prominent role in the preseason opener, their roles were drastically reduced Saturday. Williams had just one carry. Breida, who was healthy, didn't play. Some form of rookie hazing? Actually, head coach Kyle Shanahan said the two were shelved because he wanted to get a look at Kapri Bibbs and Tim Hightower. Bibbs didn't have a carry in the opener, and Hightower didn't play. "We're trying to give them a chance to compete," Shanahan said. "We see it in practice each day, but in games, you want to see what guys do, breaking through those arm tackles, and see how they perform.