NASHVILLE, Tenn. (AP) Tennessee Titans quarterback Marcus Mariota can think of only one thing that really ticks him off.

He really, really doesn't like to lose.

''Ever since I was a kid, I was a very competitive person and I don't take losing very well, and I think that's kind of what made me the player that I am today,'' Mariota said. ''So going forward, obviously, there's going to be ups and downs. You've just, obviously, got to take it on the chin and go from there.''

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The time finally has arrived for Mariota to show how much he has learned since winning the Heisman Trophy at Oregon and going to the NFL and how quickly he can make the Titans winners again. The No. 2 pick overall will be the first rookie quarterback to start the season opener in the franchise's history Sunday when Tennessee plays Tampa Bay and Jameis Winston, the top overall pick.

Titans coach Ken Whisenhunt says regardless of Mariota's gifts it would be a mistake to forget he's a rookie.

''To me, it's hard to play any position in the NFL. Once you go from college to the NFL, quarterback is even more difficult,'' Whisenhunt said. ''With that being said, we've been very impressed with how Marcus has been able to (do) it to date, and we're excited to see how he's going to progress as we go forward.''

Mariota completed 70 percent of his passes this preseason, averaging 10.9 yards per attempt - highest among all rookies. But he played to halftime of only one preseason game. So adjusting to the difference in speed from the preseason to the regular season will be an adjustment even for the quarterback who ran Oregon's up-tempo offense so very well.

He did go 36-5 in three seasons as a starter at Oregon as one of only four players in FBS history with more than 10,000 yards passing and at least 2,000 yards rushing in his career. Whisenhunt doesn't expect Mariota to need long to acclimate once the ball's snapped Sunday, and neither does the rookie even though he's noticed the difference in speed from college already.

''For us coming in just got to try to do your best to adjust to it and simplify the game so it doesn't move as fast,'' Mariota said.

Mariota says taking snaps under center may be the biggest change in his game.

''That's stuff I didn't do in college,'' he said. ''I really worked hard throughout the offseason, and these coaches have really helped me. It's come a long way, and I do feel comfortable under there and ready to go.''

Protecting the ball remains high on his to-do list. Intercepted only 14 times at Oregon, Mariota did not turn the ball over after being intercepted once and losing a fumble in the preseason opener at Atlanta.

''I got lucky with a couple plays in the last few preseason games of guys ... dropping the ball so just taking care of the football, making sure I get the right checks for our offense putting our offense in the right situations,'' Mariota said. ''All things that really I can improve on and get better at.''

Linebacker Brian Orakpo sees Mariota as a poised rookie with great leadership qualities and ''phenomenal'' pocket awareness and patience.

''I mean he does it all,'' Orakpo said. ''He doesn't get rattled. He'll throw a pick and shake it off. ... You don't see that from young guys. Usually, they're thinking about that play throughout the whole game or that series or whatever. He's onto the next play ready to go.'''

Notes: CB Jason McCourty (groin) and NT Sammie Hill (right knee) did not practice. Whisenhunt said McCourty did work out on a side field. ... New RB Terrance West, obtained in a trade from Cleveland, practiced for a second day with the team. Whisenhunt said West has worked hard since arriving and been at the Titans' headquarters a lot of hours.

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