NORMAN, Okla. — When Sam Bradford embarked on what would become a record-setting season that netted him the Heisman Trophy, it was with the deck stacked in his favor at Oklahoma.

The Sooners put a veteran offensive line, proven wide receivers and two of the Big 12's top running backs at his disposal.

Not so this year.

As Oklahoma tries to make it one step further after losing in the BCS championship game to Florida, Bradford will be relying on a new group to protect him and catch his passes in the wide-open Sooners offense that set the NCAA scoring record last season.

"I think a year ago we had a great deal of experience coming back on offense and we were going to be young and inexperienced some on defense and needed to grow. And that kind of happened as we went through the year," Sooners coach Bob Stoops said. "The offense was really pretty strong through the year and got better at the end, and then the defense got a lot better through experience through the year.

"This year, we'll probably start just the reverse."

Gone are four of the Sooners' starting linemen and three senior receivers who combined to catch 21 of Bradford's 50 touchdown passes last season.

The silver lining is that second-team All-America tight end Jermaine Gresham and massive tackle Trent Williams, who'll protect Bradford's blind side, made the same decision as the Heisman winner and opted for another season at Oklahoma. The Sooners' tailback tandem of DeMarco Murray and Chris Brown also returns after both eclipsed 1,000 yards rushing last season.

"Obviously we have some younger guys that are going to come in, but I feel like they made tremendous steps in the offseason," Bradford said. "I feel like they'll be prepared to play.

"I don't feel like I can worry about what I have to do. … I just need to do what I can to the best I can to put our team in a position to win each week."

The defense returns nine starters from a unit that ended the year a disappointing 68th in total defense. The players, and Stoops, aren't happy about that and are promising a much tougher defense this season.

"We need to just be mean," linebacker Travis Lewis said. "We're just missing that one little thing to stop people in the fourth quarter, to make that play when it counts."

Perhaps the biggest question mark as the Sooners try to add to their unprecedented three straight Big 12 titles is the line, which lost All-America guard Duke Robinson, second-round draft pick Phil Loadholt and all-conference center Jon Cooper.

Back in March, Stoops called the unit the "weak link" on the team and said the linemen needed to improve their work ethic and attitude. He came to their defense as the season neared.

"I didn't really call them out. I just get tired of having to compliment guys who haven't done it," Stoops said. "In the end, they just need time. … We'll see if they show the kind of discipline necessary to play well up there and toughness to play well."

Last year's front line paved the way for the Sooners to score 716 points and 99 touchdowns and gave Bradford the time he needed to put up Heisman-caliber numbers: 68 percent passing for 4,720 yards and 50 TDs with only eight interceptions.

But after passing up a chance to be a top pick in this year's NFL draft, Bradford wants more than the big numbers and a bronze statue.

"I want to leave the program better than when I first got here," Bradford said. "If we can win a national championship this year and be known as (Oklahoma's) eighth national championship team, that would mean the world to me."