Marcus Mariota vowed that being replaced as the Tennessee Titans starting quarterback “Isn’t going to bring me down, this isn’t going to end my career.”

His comments came this morning as the Titans confirmed that Ryan Tannehill, Mariota’s backup for the first six games this season, will be the starter for Sunday’s game against the Los Angeles Chargers.

The move had been expected since Tannehill replaced Mariota in the third quarter of an eventual 16-0 loss to the Broncos Sunday in Denver and word of the decision began leaking out late Tuesday.

Coach Mike Vrabel confirmed the change today at the Titans’ Nashville, Tenn. practice complex, saying he hoped the move would, “get a little spark” for the 2-4 Titans, who have lost four of their last five games.

“Disappointment,” Mariota told the assembled media, was his first reaction. “It is gonna be different. I haven’t really been in this role for a long time (or) at all in my career. So, again, I’m going to do everything that I can to help Ryan and help this team.”

Mariota is in the final year of his five-year rookie contract. He was the Titans’ first-round pick and the second overall selection in the 2015 NFL Draft.

Mariota said, “For me, my expectation was always to be the best player that I could be. To the day that I die, I believe that I gave all I (had). No matter what, I can learn and grow from this situation. This isn’t going to bring me down, this isn’t going to end my career. This is an opportunity for me to grow and I’m going to make the most of it.”

Vrabel said, “I am very confident that, after having talked to Marcus and watching him prepare already today that if called upon, at some point and time, we expect him to be ready to go.”

Vrabel said, “It is not an easy thing for any player. I would say it is not an easy thing for a coach that cares about his players … to make that decision. But we felt like this was the right thing for the team right now.”

Tannehill, who started 88 games at Miami before coming to the Titans in an off-season trade, had not played this season until the Denver game.

For him, too, things will change, he said. “Part of the responsibility of the backup is to kind of know your role and navigate that through meetings, thorough time on the practice field,” Tannehill told reporters. “Sometimes you do have to hold your tongue. and not speak up when you want to, so now I will be able to just be me and lead the way I want to lead and speak up and hold the guys accountable. “