Defensive lineman Bryant Young could miss the rest of the San Francisco 49ers' season after a torn ligament was discovered in his right knee Monday night. Young, a four-time Pro Bowl selection who's tied for the NFC lead with eight sacks this season, won't need surgery but will be out three to six weeks. He was hurt while tackling Seattle's Shaun Alexander in a 27-25 loss to the Seahawks on Sunday. An MRI exam revealed a complete tear of his MCL and a torn meniscus. Young, whose career has been revitalized by a move to defensive end this season, also sprained his ankle when a pile of players rolled over his leg on the play. Young, the only remaining member of San Francisco's last championship team, was on crutches when he returned to the 49ers' training complex from a doctors' appointment. He was disappointed, but hopeful he could return before the end of his most impressive year since his last trip to the Pro Bowl in 2002. "I'm staying optimistic and positive," Young said. "I'm just going to attack this rehab and get back as soon as I can."