SAN JOSE, Calif. – The San Jose Sharks are going to have to tighten things up on defense and get some production from their top six forwards if they want to remain competitive without injured centermen Tomas Hertl and Logan Couture. Top-line forwards Anthony Duclair and Fabian Zetterlund gave the Sharks a chance on Saturday as both collected two points in regulation time against the Columbus Blue Jackets. Then Boone Jenner scored with 12.9 seconds left, helping to give Columbus a 4-3 win at SAP Center. A one-handed backhand by Jenner got under and past Sharks goalie Kaapo Kahkonen, who finishe…