Defensive tackle Tommie Harris might be the best defensive player in the nation. Or maybe it’s linebacker Teddy Lehman. Cornerback Derrick Strait is another good candidate. So is safety Brandon Everage.

And they all play for the Oklahoma Sooners.

No wonder Oklahoma is the Associated Press preseason No. 1.

“We’re so deep,” Lehman says, “it’s going to be awesome to watch.”

But as Oklahoma begins working on an eighth national championship, the strength of the Big 12 Conference — especially in the South division — means the Sooners really will have to earn it.

Texas, ranked fifth, remains a prime contender, and No. 24 Oklahoma State, which has beaten Oklahoma the last two years, boasts one of the best quarterback-running back-receiver trios in the country.

Then there’s Texas A&M, which beat the Sooners during a down year last season. The Aggies expect to get a lift from new coach Dennis Franchione.

So Oklahoma fans can’t be certain they’ll be in Kansas City, Mo., for the Big 12 championship game Dec. 6.

But it’s still a good idea to make reservations.

After all, the Sooners return 10 starters from a defense that allowed fewer than two touchdowns per game last season, including one or none six times.

The Nagurski Award committee is so impressed by Oklahoma’s collection of talent that Harris, Lehman, Strait and Everage were among 36 players on the watch list for the defender-of-the-year honor. No other school has more than two.

With so much going for the defense, the burden is eased on an offense that needs quarterback Jason White finally to stay healthy and Kejuan Jones to replace 1,800-yard rusher Quentin Griffin.

“If you do not score, then you know the defense will get the ball back,” said White, a senior who has started only four games because of injuries to both knees. “There is a little pressure, but the way our offense has been working out this offseason, I think we will be just fine.”

Here are team capsules, in the predicted order of finish:

Big 12 South

Oklahoma: White has a good attitude about his health. “I feel like I’m just as capable as I used to be,” he said. “I guess I don’t have any more knees to blow out.”

Texas: Chance Mock gets first crack at replacing QB Chris Simms, but red-shirt freshman Vince Young is waiting. Their objective will be getting the ball to RB Cedric Benson and WR Roy Williams … Coach Mack Brown hopes to avoid another QB controversy like Simms vs. Major Applewhite two years ago.

Oklahoma State: The Cowboys’ combination of 3,000-yard passer Josh Fields, 1,000-yard runner Tatum Bell and 1,000-yard receiver Rashaun Woods is their best threesome since Barry Sanders was in the backfield.

Texas A&M: Franchione has gone from the 3-4 alignment of “Wrecking Crew” fame to a 4-3. He’s also sprucing up the offense, although he hasn’t decided who will run it: junior Dustin Long, coming off the second-best passing season in school history, or sophomore Reggie McNeal, who beat Oklahoma as a true freshman.

Texas Tech: QB B.J. Symons has thrown for 545 yards and seven TDs in three seasons. That’s one big game for predecessor Kliff Kingsbury, who left with 39 school records and several NCAA marks.

Baylor: New coach Guy Morriss went from 2-9 his first season at Kentucky to 7-4 last season. Now he returns to his home state trying to revive a program that has won four conference games in seven Big 12 seasons.

Big 12 North

Kansas State: QB Ell Roberson and RB Darren Sproles could post huge numbers this season considering the Wildcats might play 15 games. They have an extra regular-season game (Aug. 23 vs. California) and could play in the Big 12 championship, then a bowl. … K-State avoids OU for a second straight year, but plays Oct. 4 at Texas.

Missouri: Brad Smith became the second player in Division I-A history to pass for 2,000 yards and rush for 1,000 yards in one season, and he was only a freshman. His next trick is giving the Tigers their third winning season in the last 20. … A victory over Illinois in the opener could propel Mizzou to 5-0 for the first time since 1981.

Colorado: It’ll be a surprise if the Buffs become the first team to win a Big 12 division three straight years. They have no experience at QB and must replace 1,744-yard rusher Chris Brown.

Nebraska: The Huskers shook up their coaching staff after going 7-7, their worst season since 1961. Coach Frank Solich no longer is offensive coordinator, defensive coordinator Craig Bohl was fired and six other assistants are gone.

Iowa State: QB Chris Love and RB Hiawatha Rutland, starters coming out of spring practice, won’t play the opener after being charged with drunken driving this summer. They also can’t practice with the first team before then.

Kansas: Coach Mark Mangino heads into his second season seeking his first conference win. The Jayhawks could be in trouble if it doesn’t come Oct. 18 at home against Baylor. … A loss to Baylor last season started an ongoing seven-game losing skid.