updated 9:14 p.m. ET Aug. 27, 2009

Josh Heupel can't remember the exact moment when Sam Bradford truly stepped forward to become the man at Oklahoma. He only remembers that it happened.

Midway through last season, Heupel noticed a change in the quarterback who chose to mimic him with the same No. 14 jersey. The new Bradford went on to lead the Sooners to the BCS championship game and became the fifth Oklahoma player to win the Heisman Trophy.

"It became his football team. He took more and more ownership of it," said Heupel, the 2000 Heisman runner-up who's now the Sooners' quarterbacks coach. "He's done a much better job of grabbing our wide receivers after plays and making sure they're on the same page individually, and he's done that with other guys — offensive linemen and some of our defensive guys as well.

"That's him maturing from a young sophomore quarterback to a junior."

Bradford could just as easily be playing in the NFL somewhere, maybe even as the Detroit Lions' No. 1 overall pick. But instead he's back in Norman with one solitary goal: winning the national championship that escaped his grasp last year.

"It's all you think about, it's all you dream about," Bradford said. "And to have the opportunity to play for a national championship and come up short, it's just ... it's not a good feeling to have."

That feeling has dogged Bradford and these Sooners for seven long months, and some significant turnover on the highest-scoring offense in college football history isn't enough to lower expectations even slightly.

Four of the starting linemen who protected Bradford so well last season have finished their careers at Oklahoma, as have three top receivers who together caught 21 touchdown passes.

But tight end Jermaine Gresham and tackle Trent Williams, two other potential first-round draft picks, followed Bradford's lead and came back for another season with the Sooners. Chris Brown and DeMarco Murray, who each surpassed 1,000 yards rushing last season, are back for an encore in Bradford's supporting cast, too.

"I think that's a very comforting feeling looking out there and seeing guys who have not only been here a couple years with, but we've been in games — been in big games — with," Bradford said. "To have those guys out there that I know are great players, it makes my job a lot easier. It gives me a lot of comfort."

Bradford explains that already having a Heisman Trophy from his 4,720-yard, 50-touchdown season isn't what makes him so confident heading into this season. Instead, it's all the time it took him to earn it that keeps him at ease.

"I think what allowed him to play so successfully as a freshman and a sophomore is that he's very confident. He's very comfortable in his own skin," Heupel said. "He knows who and what he is as a person and as a football player. He comes to work every single day and finds a way to get better."

Bradford has never been one to think he's near perfection. There's always a better coverage read, a better pass, some tiny mistake somewhere that he knows he could have avoided along the way. And that drives him to keep studying and working to become even better.

"There's a lot of things that I can improve. Leadership is something that I've tried to improve every year, and I still feel like that's something that I can get better at," Bradford said. "Especially with some of the young guys that we're going to have playing this year, I think just my demeanor and the way I carry myself in practice and in games can improve and helps some of these younger guys."

His veteran teammates appreciate the example Bradford sets. Like Adrian Peterson before him, Bradford is now the team superstar who's nonetheless leading the way in team workouts, never loafing or taking a day off.

"We've got a lot of great players on this team, a lot of All-Americans, but those are the guys that are the most humble," linebacker Travis Lewis said.

And after coming so close a season ago, the only trophy Bradford and his teammates have in mind is the crystal football handed out in Pasadena in January.

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"When you think it's going good, it's never good enough. When it's bad, it's never as bad as you thought it was," Williams said. "We're never perfect. We've always got something to work on.

"No matter what, all the records set, we still were on the losing end of the national championship, so in our mind we've still got a lot to work on."

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