The Marcus Mariota era is underway in Tennessee as the Titans look to rebuild around their rookie quarterback. While the success of the team will depend in large part on how well the Heisman Trophy winner performs in his first season in the NFL, this summer has shown there are plenty of other things worth watching in Nashville.

With the regular season set to kick off Thursday, here are the five most important things we learned from the Titans' preseason.

1. Mariota appears to be the real deal

More from FoxSports

After struggling early in his preseason debut against the Atlanta Falcons, Mariota settled in nicely, completing 21-of-30 passes for 326 yards, with one touchdown and one interception and a passer rating of 102.9. There will undoubtedly be growing pains along the way, but thus far, Mariota has appeared poised and confident and looked every bit worth the No. 2 overall selection in the draft.

2. The Titans QB situation is enviable

Not only did Mariota look good in the preseason, but his backup Zach Mettenberger also did well. The second-year pro out of LSU threw three touchdowns and complied a 101.7 passer rating, prompting some to question whether the Titans should sell high and trade him to another quarterback-needy team. For now, head coach Ken Whisenhunt said the team plans to hold on to Mettenberger, potentially giving them one of the NFL's better QB duos.

3. The offensive line has a new look

After two sub-par seasons, Andy Levitre is out at left guard, having been traded to the Atlanta Falcons. He was replaced in the starting lineup by former tackle Byron Bell. Rookie Jeremiah Poutasi, a third-round pick from Utah, is the new starter at right tackle. The new group, including left tackle Taylor Lewan, center Brian Schwenke and right guard Chance Warmack, did a credible job protecting Mariota and opening up holes in the running game. Whether it carries over into the regular season remains to be season, but so far, the results are promising.

4. The Titans will be thin at cornerback to start the season

Jason McCourty, the team's most experienced corner, will miss the beginning part of the season after undergoing groin surgery. Perrish Cox, who intercepted two passes in the preseason will start at one spot, but the team will rely on Coty Sensabaugh, Blidi-Wreh Wilson and converted safety Marqueston Huff to help fill the void for McCourty to start the year.

5) Justin Hunter remains a non-factor

After earning praise from head coach Ken Whisenhunt for his play early in camp, Hunter was largely a non-factor in the preseason, catching just three passes for 24 yards. Whisenhunt has cautioned not to read too much in the third-year receiver's exhibition stats, but Hunter has been put on notice that it's time to translate his potential into productivity. The team wants to see consistency out of Hunter this season. So far, he hasn't shown it.