Mack Brown is doing double duty these days.

On top of his head coaching responsibilities, he also is attending meetings of his underachieving Texas defense and watching the unit more closely at practice.

The defense needs the help, and it's a safe bet Brown will be alongside defensive coordinator Manny Diaz in preparing for a stiff test Saturday when Texas plays at No. 20 Texas Tech, which is averaging 507 yards of offense a game.

"We have to play better on defense," said Brown, who acknowledged he's been frustrated by the unit's poor play and is working to help simplify its schemes. "We know that. The staff's not stupid."

For the first time since at least 1950, the Texas defense has allowed more than 600 yards in back-to-back games (Oklahoma and Baylor). It could end up setting unenviable school records for average yards given up and total points allowed.

Texas is No. 108 in the nation in stopping the rush and 56th in stopping the pass. The Longhorns are 96th in total defense, a far cry from finishing last season 11th .

If last week is an indication, the defense might finally be coming around. Texas gave up only 273 total yards, its second-best performance this season, in a 21-17 win at Kansas.

"Defensively, I thought there was a shot of confidence on Saturday, maybe for the first time in a long time," said Brown, who has never been a defensive coordinator. "They haven't had a lot to be proud of. They haven't had a lot to build on. This gives them something to build on."

The improvement in the comeback win at Kansas came against a team that isn't a passing threat behind redshirt freshman quarterback Michael Cummings, making the 234 rushing yards Texas allowed look a bit less impressive.

Three weeks ago, Texas senior safety Kenny Vaccaro called out his teammates, suggesting some on defense weren't playing very hard. After Texas got drubbed 63-21 by Oklahoma, he cited a "blooper reel" of missed tackles and muffed assignments.

But Red Raiders quarterback Seth Doege isn't paying attention to numbers from the Texas defense.

"I think there are times where Texas looks like world beaters on defense," said Doege, who's thrown for 30 touchdowns and 2,580 yards. "And there are times that they're not so good on defense. But I expect them to come in here, get geared up and ready to roll since it's a rival game."

Injuries have played a part. Jordan Hicks, the defense's best and most experienced linebacker, went out in the third game with a hip flexor injury. He won't play against the Red Raiders (6-2, 3-2). Next went defensive end Jackson Jeffcoat, who had a season-ending chest muscle tear.

Longhorns cornerback Quandre Diggs said things "clicked" at Kansas and the defense found a groove. He's hoping that carries over when they travel to Lubbock.

"Go out, play tough, physical. That's the main thing," he said.

When asked to rate his job performance, Diaz settled on "incomplete" because there are still four games remaining — a third of the regular season.

"For whatever we've come through, we've managed to win six games and only lose two," he said. "The players still believe in what we're doing and believe in each other. I think we're poised to finish the season on a very high note and if we do, then we can evaluate where it stands."

Red Raiders coach Tommy Tuberville has watched Texas (6-2, 3-2) struggle against the run. In four of its five Big 12 games, the Longhorns defense has allowed 234 rushing yards or more.

Texas Tech's third-year coach said he's sure Texas will continue to work on stopping the rush.

But, he said, "there is no secret to what we do. We throw it. We won't change anything for who we play."