The Tennessee Titans are taking a page from the “no duh” playbook.The Titans exercised quarterback Marcus Mariota’s fifth-year contract option Tuesday, a source informed of the situation told NFL Network Insider Ian Rapoport. The move comes after general manager Jon Robinson said on 104.5 The Zone in Nashville last week that the team was planning to exercise the option, which keeps Mariota in Tennessee through the 2019 season.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.Tennessee fired coach Mike Mularkey this offseason in large part to help unlock Mariota’s potential. The grind-out style preferred by the previous coaching staff pigeonholed a quarterback who excels in a quick-pass scheme and owns superior athleticism as a runner.