The lingering concerns about the ability of the Lions to hold up in the secondary multiplied Wednesday, when the team announced safety Louis Delmas had a surgical procedure on his left knee. The procedure was performed Tuesday by renowned surgeon James Andrews in Birmingham, Ala. Delmas hasn't been practicing and the Lions carefully guarded details of his absence. Coach Jim Schwartz said initially that Delmas was just getting rest when he missed practice last week. A four-year veteran, Delmas missed the final five games last season after injuring his right knee. Schwartz has dubbed the former second-round pick the defensive MVP, but durability issues have prevented the 25-year-old from having that type of consistent impact. In 41 career starts, he has 163 tackles, three sacks, two interceptions and two forced fumbles.