While Mariota can make all of the throws expected of an NFL signal-caller, he lacks the ability to elevate his supporting cast. The Titans have finished 9-7 for three straight seasons with him under center, and they have only one playoff victory throughout his four-year career.
Instead of trying to extend Mariota this offseason, the Titans picked up the fifth-year option on his rookie contract. They'll undertake a wait-and-see approach this fall before deciding whether to commit to the 25-year-old beyond this season.
Head coach Mike Vrabel recently spoke about that situation, per The MMQB's Robert Klemko:
"I think everybody has a contract, and we're very aware of players who are in the last year of the deal. Marcus is obviously one of those. When you make a commitment to the QB, you want to make sure that this is going to be your guy for the next 7-10 years when you look at the percentage of the cap quarterbacks are driving.
"Nobody is more proud of what Marcus has done in the offseason than me. He's come back stronger, bigger, with greater understanding of what we're doing offensively, being able to communicate it to players the field. I don't look at the lack of a long-term extension as a negative, though that's what people try to make it. I know Marcus's demeanor, and that won't change whether he's on a 10-year contract or its up after the season. He's that type of person. So I know it'll work because of how he is."
Vrabel might not see Mariota's lack of an extension as a negative, but it isn't a positive, either.
When drafting a quarterback that high, teams hope to achieve long-term stability by finding a signal-caller who deserves a hefty extension. Instead, Mariota and 2015 first overall pick Jameis Winston will be the first two quarterbacks under the current CBA to play out their full five-year rookie deals.
Numerous factors contributed to Mariota's lack of growth, including multiple injuries, coaching changes and a poor supporting cast. However, those excuses no longer matter since Tennessee soon must decide whether to hand him a massive contract.
Tennessee changed offensive coordinators this offseason for the fourth time in the past five years, but Vrabel promoted tight ends coach Arthur Smith to the position. Familiarity was a deciding factor in Smith's ascension.
"Since Marcus has been here," Vrabel said in January, per the Tennessean's Erik Bacharach, "he's seen Arthur."
Smith spent eight seasons on the Titans staff through four different regimes before becoming the offensive play-caller. He understands the significance of continuity.
"He's already changed enough," Smith said of Mariota, per PaulKuharsky.com. "So, when he comes in here, he'll know exactly how we're reading plays, he'll know exactly how we're calling plays. It just allows him to take another step ... I think as the whole offensive improves in Year 2, it will help the quarterback."
While Smith's promotion will add an extra layer of comfort, it may only accentuate Mariota's previous flaws.
Certain quarterbacks are great working within the constraints of their team's offensive scheme, such as Minnesota Vikings signal-caller Kirk Cousins. He can identify exactly where he needs to go with the ball and make the right throw. As such, Cousins serves as the baseline for mediocrity because he isn't expanding upon the scheme's capabilities.
A quarterback should be lauded for consistently making correct reads and throws, but the NFL isn't played in a confined manner. Breakdowns occur. Individuals make plays. Live-action performances become messy and don't always reflect play designs. Greatness emerges from the wreckage of the preordained.
Mariota's mental processing became his greatest strength at the University of Oregon. Coupled with outstanding athleticism often utilized in designed run plays, he can be efficient and accurate.
He has yet to mature beyond that point, though. In Tennessee, he has floundered without a suitable supporting cast.
The "exotic smashmouth" system set the Titans back years. Instead of trying to accentuate Mariota's style, the front office and coaching staff decided a physical, run-first approach was the right path. Mariota struggled in the passing game because the Titans lacked players who could create after the catch.
Wide receiver Corey Davis, the No. 5 pick in the 2017 draft, is only part of the solution.
This offseason, the Titans bolstered their receiving corps by signing Adam Humphries and spending a second-round pick on A.J. Brown. They also upgraded their offensive front by signing veteran Rodger Saffold and drafting Nate Davis in the third round.
However, those same additions could serve as an indictment of the quarterback position.
If Mariota is only as good as those around him, he's isn't a franchise-caliber quarterback. As Vrabel said, the Titans someone to fill the position for the next 7-10 years, not just another cog in the machine. They could get the latter from backup Ryan Tannehill.
Tennessee won't receive any help from the other AFC South members, either. The Indianapolis Colts appear capable of a Super Bowl run. The Jacksonville Jaguars should bounce back after a down year since they signed a competent quarterback in Nick Foles. The Houston Texans won the division a year ago with the NFL's worst offensive line.
Meanwhile, the Titans are arguably the AFC South's worst team heading into the 2019 season.
Something is missing in Tennessee, and Mariota is less than a year away from entering bust status if he can't stay on the field and drastically improve this fall.