All-American, Heisman Trophy winner, first-round draft choice … the expectations were lofty for Marcus Mariota since draft day.

What he did Sunday in his debut has only heightened them. And if you listen to his teammates, for whom he sets the tone in his rookie year, that is a good thing for a team that had lost 22 of its past 28 games prior to his arrival.

In the wake of Mariota’s record-setting four-touchdown first-half performance in the season-opening victory over Tampa Bay, offensive tackle Taylor Lewan, the clubhouse go-to guy on most things Mariota, said, “I think the thing now is to keep taking it, keep moving forward and understand he set the bar pretty high (in) his debut. And, now, we have to keep on keeping on.”

Let’s not forget the downtrodden Titans gained access to the No. 2 overall pick in the April NFL Draft by virtue of their 2-14 record in 2014, a season in which they were 29th in the 32-team league in scoring.

They invested the franchise’s highest pick in 31 years — and upwards of $24 million over the next four years — in the fervent hope that Mariota could help lift them back into the playoffs, a place denied them since 2008.

Nobody is talking playoffs — out loud at least — yet for 2015, but in the soft spoken, charismatic 21-year-old from Hawaii it is apparent the Titans see a new world of possibilities opening up to them.

Lewan said, “He’s a great football player. His mentality is there. I’m just excited to block for him. I know guys are nervous about him running and stuff like that, but to be that guy’s left tackle and for him to have the debut that he had, I feel partly responsible for that. I know his offensive line does, and it’s exciting to have that kind of production.”

You get the sense that the Titans bought into Mariota early on as the fresh new face of the franchise, partly in tribute to his skills and manner but also because the organization had so fully staked its future to him.

Much as Tampa Bay, another 2-14 bottom feeder from 2014, had bet its future on quarterback Jameis Winston, the draft’s overall No. 1 selection.

But players will tell you that simply being a high draft choice and arriving with loads of potential means very little until it is realized on the field.

Few have known that as well as Titans fans, who have seen highly touted quarterbacks Vince Young and Jake Locker come through Nashville in recent years with major fanfare and little in the way of results to show for it.

Which is why what Mariota displayed Sunday was the most important affirmation for them, the one that came under fire. Sooner rather than later. As much as some say they saw it coming, seeing was believing when it came in a full-speed regular-season opener.

“The guy has a lot of confidence, a lot of poise,” running back Bishop Sankey marveled. “He doesn’t carry himself like a rookie at all.”

Which is why the Titans are hoping he can carry them far.

Reach Ferd Lewis at flewis@staradvertiser.com or 529-4820.