A football commemorating that team sits above Mariota’s bed at home, but most of his room is a shrine to his accomplishments at Oregon.

Yet his college career, like his high school career, did not start so smoothly. He redshirted his first year and felt homesick. His quiet demeanor was misunderstood.

“Some of the coaches on our staff didn’t like him because he literally did not say a word,” said Helfrich, who became the Ducks’ coach in 2013 when Chip Kelly left for the N.F.L. “He just kind of deferred to the elders on the team from a leadership standpoint. That turned some people off. ‘Hey, can this guy really lead us?’ ”

But this time, when Mariota faced a quarterback competition, he seized the job over a player a year ahead of him.

Last season, Oregon finished 11-2 over all and 7-2 in the Pacific-12 Conference, losing to rival Stanford for a second consecutive year.

A sprained knee ligament limited Mariota against the Cardinal, and Oregon trailed at halftime, 17-0. Mariota raised his voice in the locker room, challenging his teammates for more effort. The Ducks rallied to score 20 points in the fourth quarter but ultimately fell short, 26-20. The loss knocked Oregon out of title contention and Mariota out of the Heisman picture.

Mariota’s parents met him outside the visitors’ locker room, and he collapsed into his father’s arms sobbing.

A few weeks later, Mariota huddled with his family in Eugene and decided to return to Oregon for another season. Had he left early for the N.F.L., he almost certainly would have been a first-round pick. His career goal was within reach. But by now, he had matured enough to know himself. He wanted to graduate, and, he concluded, he was not ready for the next step.