The Sharks addressed their depth on defense by signing unrestricted free agent David Schlemko to a four-year, $8.4 million deal on Friday. Schlemko is a versatile left-handed rear guard who can play in all situations, including on a second power-play unit and the penalty kill. “I’m lucky a Stanley Cup contender wanted me,” said the 6-foot, 190-pound Schlemko, who has 15 goals and 54 assists in 298 regular-season games.