Jets running back Curtis Martin, fourth on the NFL's career rushing list, announced his retirement Thursday -- 19 months after playing his final game. The five-time Pro Bowl selection acknowledged in January that he had probably played his last game because of a bone-on-bone right knee injury suffered during the 2005 season. Martin made the long-anticipated decision official -- after months of rehabbing and deliberating -- a day before the Jets begin training camp practices. "I don't see this as a sad time," Martin said at a small, 45-minute news conference at the team's Manhattan offices, one of several stops on a whirlwind media tour. "Someone was just asking me if there's any moment in particular that sticks out as the best moment of my career, and I told them, 'Right now."'