ALAMEDA — The Oakland Raiders re-signed offensive lineman Langston Walker on Wednesday and waived fullback Oren O’Neal with an injury.

Walker was a second-round pick by Oakland in 2002 and spent his first five seasons in the NFL with the Raiders. He left to sign a five-year, $25 million contract with Buffalo before the 2007 season and was cut by the Bills the week before this season started.

The Raiders need help on an offensive line that has been hurt by injuries to left guard Robert Gallery and right tackle Cornell Green.

Erik Pears started three games, first at guard and then at tackle last week. Pears has struggled, committing four false starts already to tie for the league lead in that category.

The Raiders had three players starting at different positions last week than they had in the opener, with center Chris Morris moving to left guard, backup Samson Satele starting at center and Pears at right tackle.

“We’ll see if he can get in and learn the system, and see if he can do our system,” coach Tom Cable said. “He certainly wouldn’t be able to do it this week. Maybe in a week he’ll have a chance to, get enough practice.”

Walker’s weight is down from 380 pounds to about 362, Cable said, which is still very big for a zone blocking lineman who needs to be athletic enough to get upfield to make blocks.

Walker came in for a tryout last week and the Raiders waited a week before deciding to bring him back for a second stint. Walker has mostly played in a power-blocking scheme and will have to learn the zone system employed in Oakland.

“It’s slightly different, but I think I can do it. I’m athletic enough. I guess if I couldn’t they wouldn’t bring me in,” he said. “I think it’s more about learning the playbook. That’s the biggest issue standing in front of me. Different words and signals and nomenclature, and different quarterback.”

Walker, who was born in Oakland and played in college at nearby California, said it was difficult to leave the Raiders two years ago but he couldn’t turn down the money the Bills offered in free agency.

“It was real tough. This has always been my childhood favorite team, but business is business,” he said. “We all know how the NFL is.”