(Nashville, TN)  --  Former Duck Marcus Mariota is not a lock to start Week One for the Tennessee Titans, according to reports.  According to ESPN, there is a groundswell for former Dolphin Ryan Tannehill to possibly be under center September 8th when they face the Browns in Cleveland.  Head coach Mike Vrabel has said Mariota is the starter and Tannehill is there to push him, but the former Heisman Trophy winner is entering the last year of his rookie deal and the club has not offered him an extension.