Marcus Mariota says he is under no illusions that he will be back-up quarterback to Derek Carr at the Las Vegas Raiders.

The 26-year-old penned a two-year highly incentivised contract with the Raiders, with his base 2020 salary said to be guaranteed at $7.5million and another $5.9m in potential add-ons.

Mariota won the coveted Heisman Trophy in 2014 but largely struggled during five seasons with the Tennessee Titans and lost his starting berth to Ryan Tannehill last season.

Speaking about his move to the Raiders, Mariota says he wanted to join a team that can bring out the best of his abilities even if for the time being he is behind Carr in the pecking order.

"First and foremost, this is Derek's team, and I understand that," Honolulu native Mariota told Hawaii-based KHON-TV.

"I understand that going in. My priority going into free agency was to be a part of a team that I felt could bring out the best in me. 

"Whatever happens, whatever comes of that, I'm ready for. But I do know, to play starting quarterback in the NFL, to be at that spot, is not an easy job to do. 

"And I think, when it comes down to it, a strong, stable supportive quarterback room makes that job a whole lot easier, and that's what we have to do. 

"And I'm going to do my best to support Derek in every possible way that I can, and along with that, I'm just going to try to become the best player that I can be and see where that takes me."

The Raiders went 7-9 last season and were officially renamed the Las Vegas Raiders in January.

Carr, 28, started 16 games for the Raiders last season, throwing for a career-high 4,054 yards, and is under contract through the 2022 campaign.