"He's got those (knee) braces off, and he's flying around," Casey said on Friday's edition of NFL Network's NFL HQ. "I think he's learned the playbook a lot better, and he's going to come out there and lead ... hopefully we make it to the playoffs this season."
Stressing that Mariota is the "definition of a true leader," Casey is the latest in a long line of Titans expressing the utmost confidence in the precocious quarterback's ability to lead the organization out of the dark ages.
New offensive coordinator Terry Robiskie has raved about Mariota as a "special talent, a special guy, a special player."
Whereas Mariota was hindered by a league-worst supporting cast last season, his surrounding talent has a strong case as this year's most improved.
"When (Henry) first walked in, I thought he was a D-end," Casey quipped. "But he's a straight running back, and he's got the speed of a running back."
Casey expects to finish with a top-five defense this year after ranking 12th in yards allowed in LeBeau's Nashville debut.
All 32 teams are optimistic in June. The Titans are counting on a host of young players to realize their potential, but the talent is certainly there to mount a serious charge at the division title in a wide-open AFC South.