Detroit Lions safety Louis Delmas left Sunday's game in the third quarter and is scheduled to undergo tests to determine the severity of his left knee injury. Delmas missed the first four games of the season with a left knee ailment, but the Lions didn't disclose the exact nature of that ailment. Delmas underwent a surgical procedure on his knee on Aug. 7 and was sidelined for more than eight weeks. Head coach Jim Schwartz has been protective of Delmas in the past, calling him the team's "top defensive player" and vowing to not rush him back from the training camp knee issue. Without Delmas, the Lions' secondary hasn't been the same. Detroit has three interceptions -- one by Delmas -- while quarterbacks have completed 64.1 percent of their passes with 10 touchdowns.