SAN DIEGO — The San Diego Chargers have placed defensive tackle Jamal Williams on injured reserve with a triceps injury, meaning he'll miss the rest of the season.

It's a big loss for the Chargers. Although the 12-year veteran has a history of knee injuries, he's still been a force in the middle, particularly against the run.

William's backup is Ogemdi Nwagbuo, who spent five weeks on San Diego's practice squad last year. To fill Williams' roster spot, defensive end Andre Coleman was signed from the practice squad.

The Chargers already are without running back LaDainian Tomlinson and center Nick Hardwick for Sunday's home opener against Baltimore. Both have sprained ankles. Also, backup defensive end Travis Johnson is out with a groin injury.