updated 8:14 p.m. ET Oct. 11, 2008

DALLAS - Linebacker Ryan Reynolds had been as close to perfect as any defender in Bob Stoops’ time at Oklahoma.

When he went down with a season-ending knee injury, the top-ranked Sooners — and perhaps their championship hopes — went with him.

Reynolds’ injury prompted a sudden collapse in Oklahoma’s defense, as the No. 5 Longhorns (6-0, 2-0) scored on their next four possessions — including three touchdowns — to pull ahead for a 45-35 victory and the early edge in the Big 12 South race.

“He brings consistency, he brings leadership, he brings everything,” said linebacker Travis Lewis, a first-year starter who’s been mentored by Reynolds. “Just having him out, that takes away from our defense.”

Against Baylor last week, Reynolds became the first player in defensive coordinator Brent Venables’ memory to grade out at 100 percent, meaning he lined up correctly on every play, wasn’t seen loafing on any plays and generally did all the little things right.

Reynolds had three tackles over the first two-plus quarters against Texas, helping the Sooners to a 28-20 lead. But after Longhorns tailback Chris Ogbonnaya picked up six yards on an early third-quarter run, Reynolds remained on the ground. Trainers attended to him, and he walked slowly to the sideline and took a seat on a trainers’ table.

Texas, which had gone three-and-out on its opening second-half possession, marched 89 yards for a score immediately after Reynolds’ injury and didn’t get stopped again until it had a 10-point lead with less than a minute to play.

In the meantime, Oklahoma got the news that Reynolds wouldn’t be returning. He’s out for the rest of his junior season with a torn anterior cruciate ligament in his right knee. He’s already overcome two torn ligaments in his left knee, one in spring 2006, another in spring 2007.

“Hearing what happened to him, I was crushed,” Lewis said.

Reynolds, the Sooners’ only returning starter at linebacker, helped get Lewis and Keenan Clayton ready for the season. He’d make sure they were in the right positions before plays.

“Ryan’s been a major force for us and leader and an excellent player for us,” Oklahoma coach Bob Stoops said. “It impacted us.”

The Sooners had more problems than just Reynolds’ devastating injury. They couldn’t corral Colt McCoy, and he repeatedly scrambled for gains or to find receivers downfield. And when they just couldn’t afford to bend anymore, Ogbonnaya had the longest run of his career — a 62-yarder that set up the clinching touchdown.

“There were a couple of critical third downs where we weren’t able to get off the field,” Venables said.

The Longhorns converted 6 of 13 third downs and also capitalized on a slew of Sooners penalties. Lewis was twice flagged for hitting McCoy after he’d gone out of bounds, and the Sooners also jumped offsides four times — resulting in two Texas first downs.

“We just have to have better poise and discipline, and we as coaches have got to get our guys to play smarter,” Venables said.

Greg Davis, the Longhorns’ offensive coordinator, thought the plays leading up to those third downs were just as crucial. While Texas wasn’t having any success running the ball earlier, he tried to make up for that with short passes.

Eventually, that helped free Ogbonnaya for the game-breaking run.

“I think it’s patience and execution,” said Ogbonnaya, who ran for 127 yards on 15 carries. “They’re a great football team ... but we wanted to just keep working through everything. Slowly but surely, the momentum started shifting our way and when we got it, we didn’t want to let it go.”

Venables said he’ll use several players to replace Reynolds. Redshirt freshman Austin Box may move from the outside, where he has been a reserve, although he’s never played in the middle. Brandon Crow filled in Saturday.

Regardless, the Sooners will face No. 16 Kansas next week with three linebackers who’d never started before this season.

No matter who is in there, the rest of the Sooners can’t make excuses. They still have one of the most loaded defensive lines in the country — especially after tackle Demarcus Granger returned from a foot injury Saturday — and a secondary that’s maturing quickly.

“This is not a one-man team at all,” Lewis said.

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