Marlin Jackson left practice Tuesday with a ruptured Achilles tendon in his right leg, the Philadelphia Eagles announced, leaving the team even thinner at free safety. Jackson, who signed a two-year contract with the Eagles as a free agent, is coming off two season-ending knee injuries he sustained with the Indianapolis Colts. He missed the second half of 2008 with a torn anterior cruciate ligament in his right knee and returned in 2009 before tearing the ACL in his left knee during a November practice.