SANTA CLARA, Calif. — The worst fears about San Francisco 49ers running back Thomas Clayton were confirmed Sunday. His season is over because of a torn anterior cruciate ligament in his right knee, suffered in Friday night’s exhibition opener against Denver.

What’s less clear is if his 49ers career is done, too.
The team placed him on the waived/injured list, which means he can be claimed by another organization. But if he clears waivers, as expected, he will revert to the 49ers’ injured reserve list.
The 49ers made that procedural move because they suddenly are down in running backs and it created a roster opening. They used it to sign Bill Rentmeester, a rookie fullback from Wisconsin waived Aug. 5 by the San Diego Chargers.
Coach Mike Singletary also said fullback Zak Keasey will be out eight to 10 weeks because of a fractured forearm.
The 49ers are taking a wait-and-see approach on Clayton’s long-term future with the team, assuming he isn’t claimed. Singletary was disappointed to see the hardworking Clayton, who led the team in rushing the past two preseasons, go down.
“It’s always unfortunte when you lose anyone, but this is a guy who gives you everything he has, every down,” Singletary said. “”& When you look at him on film, you know he’s going as fast and as hard as he can go.”
The 49ers aren’t exactly hurting at running back. Rookie Glen Coffee, who rushed for 67 yards on 14 carries Friday, looks like a strong backup to Frank Gore.
“The biggest thing that sticks out with him is that he doesn’t play like a rookie,” Singletary said. “He doesn’t carry himself like a rookie. He plays with an attitude. He’s a very tough kid.”
—After being off Saturday, the players returned to the field Sunday with a light walk-through. Singletary said the team went over mistakes made in the victory over the Broncos.
Today it’s back to the grueling work, and the good news is some familiar faces also will be back. Linebacker Patrick Willis (ankle) and tight end Delanie Walker (concussion) are expected to practice. Cornerback Tarell Brown (toe) will resume running.
—The 49ers and Raiders meet Saturday, and arguably the two biggest names in Bay Area pro football — Singletary and Oakland managing general partner Al Davis — apparently don’t know each other very well.
Singletary said their only contact came when he was playing with the Chicago Bears. Davis, he said, always made it a point to be on the field before the game so he could talk with opponents.
“He would treat them like they were his own players,” Singletary said. “He would be like, ’Hey, how are you doing? What’s going on?’ He was very nice. The Raiders were the only team in the league who did that. They treated you very well before the game.”
Then he paused.
“But it went downhill after the game started,” Singletary added.