It was only Marcus Mariota’s first on-the-field day of rookie minicamp in Tennessee Friday and already the battle for the Titans’ starting quarterback job is officially on.

Gentlemen, start your offenses. 

Never mind that the field at Saint Thomas Sports Park belonged to Mariota  — and the 37 media on hand to chronicle his debut — on this day, the battle with Zach Mettenberger for the reins in 2015 has begun.

Two days earlier Mettenberger, last year’s starter, had served notice he does not intend to go quietly to the bench, pledging a "fight to the death" to keep the starting job.

Mettenberger told ESPN’s Adam Caplan:  "I don’t (know) what the (coaches’) mind-set is, but at the end of the day I can just control what I do and I’m extremely confident in myself, almost to a fault. But people who know me know I’m not going down without a fight to the death." 

Told of the vow, Mariota embraced the challenge. "I’m going to have the same mind-set," Mariota told reporters after practice. "Overall, I think together that will make the team better. Competition will drive this team."

Characteristically, Mariota lauded his rival, saying, "I’ve gotten to know Zach (in the week at Titans’ headquarters). Zach’s an awesome guy, he’s helped me out since I’ve been here. I think as this process goes on we’ll be able to push each other and make this team better."

It was the same approach Mariota took as a redshirt freshman in the spring of 2012 when he set about unseating the more experienced Bryan Bennett, the heir apparent for Oregon’s starting quarterback position.

This time, of course, Mariota is the widely-displayed face — and fervent hope — of a struggling franchise that has not been to the playoffs since 2008.

Titans’ head coach Ken Whisenhunt made that clear three weeks ago on the first day of the NFL Draft, when Tennessee took Mariota with the second overall pick, that the Saint Louis School alum was the expected opening game starter Sept. 13 at Tampa Bay.

Hardly surprising since the Titans turned down offers of a trade for a handful of draft picks and some current players to take Mariota and are expected to invest $21 million in a four-year guaranteed contract.

Mettenberger, a sixth-round pick out of Louisiana State in 2014, started six games and looked to be 

No. 1 in 2015 with the abrupt postseason retirement of Jake Locker. He campaigned for the opportunity last fall and won a following in Tennessee with his strong arm and toughness before going down with a shoulder injury in December.

But the 2-14 Titans, who went 0-6 with Mettenberger at the controls, took a long look at the position in the offseason and the more they saw of Mariota in their pre-draft talent search, the more they liked him.

Friday, Whisenhunt said, "I didn’t hear the ‘fight to the death part,’ but, yeah, that’s what you want (Mettenberger) to say, right? You want him to be competitive."

For as long as this budding Titanic struggle lasts, anyway. 

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