The Tennessee Titans are taking a page from the “no duh” playbook.General manager Jon Robinson announced Wednesday on 104.5 The Zone in Nashville the team plans to exercise the fifth-year option for quarterback Marcus Mariota, which will keep him in Tennessee through the 2019 season. The option is guaranteed for injury only.The deadline to officially employ the fifth-year option is May 2.The No. 2 overall pick in 2015 was never going anywhere.The Titans franchise cornerstone, Mariota owns the traits to be among the top signal-callers in the NFL for the next decade. The biggest concern for the 24-year-old quarterback is health. Mariota has yet to play a full 16-game regular-season slate in his three-year career.