The ISU defense has been playing from behind the eight ball all season.

Replacing eight starters from their record-setting 2005 defense was a big enough challenge, and now the Cyclones are forced to make adjustments again.

Iowa State lost senior cornerback DeAndre Jackson for the season with a knee injury in Saturday’s loss to Oklahoma. This injury comes just two weeks after linebacker Adam Carper went down for the year with a knee injury of his own.

The defense that returned three starters is now down to one.

Brent Curvey is the only full-time starter from that 2005 defense that is still available.

So when coach Dan McCarney had all eight scholarship players in the defensive backfield stand up in front of the team during Sunday’s team meeting, the significance of the moment was heightened.

“You’re on scholarship, step it up,” McCarney said to his defensive backs. “Bow your necks. Start helping this team more.

“There are a lot of people who have faith and trust in you, but it’s not about talking about it. It’s about going out and doing it.”

A message from a coach doesn’t get any clearer. It’s now or never.

The Cyclones are 0-3 in the Big 12 for the fourth consecutive season. Although Iowa State has come back to make a bowl in its last two years, the Cyclones haven’t had a defense struggle early as much as this one has.

“He was telling us that it was our time to step up,” cornerback Chris Brown said. “We’re going to have to help the team get to a bowl game, that’s our whole focus right now. We just have to step up.”

Brown is listed on the two-deep as a backup cornerback, but he will see plenty of snaps against a Texas Tech team that runs a high-powered fun-and-gun offense.

The Red Raiders lead the Big 12 in passing, averaging nearly 340 yards a game through the air.

“They’re a crazy passing attack,” Brown said. “They throw the ball all over the place.”

Conversely, Iowa State is No. 10 in the conference in pass defense.

With Jackson out for the season, redshirt freshman Steve Johnson has moved from safety to cornerback where he will team with sophomore Chris Singleton.

Sophomore Jason Harris – a running back last year who was moved to the defense in preseason practice – is listed to get the start at Johnson’s former position of free safety.

“Since our best cornerback is gone, now we have to step up and make plays,” Singleton said.

Jackson led Iowa State with five interceptions last season, making his mark as the team’s best corner and teaming with the graduated LaMarcus Hicks to shut down opposing defenses. A four-year player and defensive captain, Jackson was the glue that held the defense together.

“Dre was a big brother to me on the field,” Singleton said. “I would look at him, ask him what I was doing wrong, what I can do better on the field. Now with Dre gone, I have to be the leader so I have to go make plays.”

None of the new depth chart changes is permanent, McCarney said.

Each spot in the defensive secondary is up for grabs, with the player at each position who plays the best in practice getting the start on Saturday.

Iowa State will also get a boost with the presence of redshirt freshman James Smith.

After breaking his ankle in the preseason, Smith has worked his way back, doing some things in practice but has not been ready for a game.

Now Smith is back on the depth chart, working behind Caleb Berg.

“It’s all about practice,” McCarney said. “We want to watch him practice and see if he’s ready to go. If he is, he’ll play, but if he’s not, he won’t. It would sure be nice to get him back.”