Guard Larry Allen, sidelined since suffering a knee injury in the opener at Arizona, practiced Wednesday but remains doubtful for Sunday's game against the Chargers. Allen also practiced last Wednesday but was forced to back off the next day because of recurring soreness.

Coach Mike Nolan said he was hopeful that Allen's condition improves the rest of the week, but the probability remains that he won't return until the Chicago game Oct. 29 following the 49ers' bye week.

Meanwhile, left tackle Jonas Jennings was held out of practice after undergoing surgery Monday to reattach a torn ligament in his left pinkie finger. He was listed as questionable.

Adam Snyder worked both at left tackle and left guard. Allen and Tony Wragge also saw time at left guard.

Linebacker Derek Smith was held out of practice because of a hip flexor injury. He remains probable for the San Diego game.