NORMAN — This isn't a typical Oklahoma defense.
The Sooners are ranked 80th nationally in total defense and still haven't faced some of their biggest tests.
Starting with Colorado on Saturday, OU will face four of the conference's top running backs in five weeks. But the toughest challenges will be the final three road games, when the Sooners face three of the nation's top offenses.
Four times OU has allowed more than 420 yards. Missouri compiled 486, including 178 rushing yards.
"It's stuff that plagued us before the Iowa State game — big plays, missed assignments and poor tackling," said defensive end Jeremy Beal. "We've got to get those things fixed. If we get those fixed we'll play pretty good defense."
Colorado's offense has struggled much of the season, but running back Rodney Stewart's 652 yards rushing rank fifth in the league.
"There are a number of things we can be better at, particularly stopping the run," said defensive coordinator Brent Venables. "Those guys inside are fighting like heck and doing everything they can. Other guys around them have to do a better job, too."
It's obvious the Sooners miss defensive tackle Gerald McCoy, the No. 3 pick in last year's NFL Draft. Adrian Taylor hasn't fully recovered from ankle surgery. And with Casey Walker (knee) and Daniel Noble (ankle) out with injuries, the Sooners are playing only three defensive tackles — Jamarkus McFarland, Stacy McGee and Taylor.
"We've forgotten about Gerald a long time ago," Venables said. "He's not making any more plays for us. Guys are working hard, trying their best. We're trying to find the best combination of guys that can help us. Some of the issues in the run game weren't really necessarily those guys.
"Some of it was we were in some bad calls. That's not on them. The ownership has to go around. The accountability has to go around. Close to half of (Missouri's rushing) yards our guys were at a disadvantage because we were in difficult calls. Sometimes we make bad calls believe it or not."
OU also failed to generate a pass rush against Missouri quarterback Blaine Gabbert. Against spread teams, three guys can get worn out chasing the quarterback play after play.
"Obviously depth is going to help you rush the passer up front if you have it," Venables said. "We don't right now so we have to be creative and find other ways to create that pressure."
The Sooners had some success with a 3-4 package, inserting backup weakside linebacker Corey Nelson. Would the Sooners also consider blitzing more?
"If you start bringing people you have less guys in coverage. You're more vulnerable," Venables said. "There's a delicate balance. We have to find ways to be better at both. But it all starts first and foremost with the run game. If they're able to run the ball you have to put more guys in (the box) and fewer guys in coverage."
Generating a pass rush will be critical when the Sooners face spread offenses like Oklahoma State, Baylor and Texas A&M. All three are balanced, capable of running and throwing.
"The secondary can't cover all day," Beal said. "When the D-line doesn't get any pressure it's harder on them. That's why (Missouri) picked us apart. But we have to put it behind us. You watch the film and you move on."
In the bottom line category, the Sooners rank 44th nationally in scoring defense (21.4). But if the defense doesn't improve it could force the offense to win some shootouts the final month of the season.
"When they spread you out, it's all of us working together," said cornerback Demontre Hurst. "The D-line has to get a pretty good pass rush. The linebackers and DBs have to get a body on receivers, mess up the timing on their routes and not let them run free. It's all of us working together."
Big 12 leading rushers
1. Kendall Hunter, OSU;147.3
2. Daniel Thomas, K-St.;127.9
3. Taylor Martinez, Neb.;124.3
4. DeMarco Murray, OU;101.7
5. Rodney Stewart, Colo.;93.1
6. Jay Finley, Baylor;87.1
7. Christine Michael, A&M;84.6
Game by game breakdown of yards and points allowed by Oklahoma's defense: