Linebacker Manny Lawson will miss the rest of the 49ers' season after tearing a ligament in his left knee. Lawson, a starting outside linebacker in the 49ers' 3-4 defensive scheme, went down with the injury during Wednesday's practice. The injury didn't initially appear to be serious, and Lawson rode on a stationary bike for the rest of the team's workout. But tests determined Thursday that Lawson tore his anterior cruciate ligament.