Iowa State faces another stiff challenge Saturday in its schedule with a trip to Norman, Okla. to face No. 6 Oklahoma.

The Sooners (5-0, 1-0 Big 12) are 24-point favorites over the Cyclones (3-3, 1-1), who will be facing a top-10 team for the second straight week.

At the midpoint of the season, the caliber of the opposition isn’t always the biggest problem. The team that will take the field Saturday in Norman is tired and beaten up.

“The grind’s getting there,” said ISU sophomore linebacker A.J. Klein. “Just the body is starting to wear down a little bit as the season wears on.”

Klein and fellow linebacker Jake Knott have been on the field for nearly every snap this season. The two are far and away the team’s tackling leaders — Klein is 13th in the nation — and are the most consistent playmakers on an ISU defense that is ranked No. 97.

Being on the field for every play of the ball can wear on a young body — they’re both just sophomores in their first full year of competition — but they’ve taken on the responsibility of leading the young defense.

“We wouldn’t have it any other way,” Klein said. “We want to be playing every snap. I want to be in there and help this team win.”

Klein, Knott and the rest of the ISU defense will likely be called on a lot during Saturday’s game with the Sooners.

Oklahoma’s offense is just the 40th best in the country, but not for lack of trying.

The OU offense is led by sophomore quarterback Landry Jones, who has one of the nation’s top receiving threats in Ryan Broyles. Broyles is eighth in the country with 103 receiving yards per game and has four of Jones’ 11 touchdowns.

The Sooners, under 12-year boss Bob Stoops, also run one of the country’s quickest offenses.

“They’ll spread it out on you, they’ll run it down your throat, they’ll do a lot of different things,” Klein said. “They do a lot of hurry up. They’re really quick.”

Oklahoma’s hurry-up offense could spell trouble for the tired ISU defense.

ISU defensive coordinator Wally Burnham said that at one point during the season the Sooners ran a series of four plays in less than one minute of game time and has averaged 85 plays per game this season.

In the last two weeks alone, the ISU defense has gone up against 166 snaps of the ball and has faced an average of 71.5 per game this year.

“It’s a real concern,” Burnham said.

There’s a lack of depth at linebacker that was made worse by the injury to Matt Tau’fo’ou earlier this year. The depth isn’t much greater at any other defensive group, either.

At linebacker, though, it seems that Knott and Klein would need to step off the field at some point, particularly against the fast-paced offenses that have been on the ISU schedule.

“I can’t find a place,” Burnham said. “The other kids are not quite where they need to be to get in and do consistently what needs to be done.”

Burnham’s unit isn’t the only one banged up on the Cyclones’ trip south.

Offensive coordinator Tom Herman will likely do most of his play calling this week without running back Alexander Robinson. Robinson has been suffering from an ankle injury, but also injured the same foot against Utah and is likely to be held out of the game.

If Robinson does see the field, it will likely be 10-15 snaps and even fewer touches of the ball.

In the place of Robinson will be a tandem of freshmen. True freshman Shontrelle Johnson has been garnering most of the buzz and has 24 carries for 179 yards, 61 of which came on a touchdown against Texas Tech. Herman said that Johnson’s running style is similar to Robinson’s, so many play calls can be used well for both backs.

The other will be redshirt freshman Jeff Woody, who is much more of a power-type back.

“Jeff will get you those inside, tough yards,” Herman said. “That may be the only difference, when Jeff’s in there some of the runs may be a little different.

The success of the ISU running game will be tied to the outcome of the game. Oklahoma’s defense is just 93rd in the country and 79th against the run, but the unit has still found a way to keep opponents to 22.8 points per game.

“They’ve got one of the best defensive ends in the league and one of the best secondaries in the league,” Herman said. “They don’t have to do a lot of things to wreak havoc, they can do it with their normal base defense, so that’s going to be the biggest challenge.”

Preparing for Oklahoma — and a trip Oct. 23 to Austin, Texas, to face the Longhorns — has caused coaches to change up practice routines.

Tuesday, Herman said the team practiced in just helmets and shorts, not their customary practice pants, which seemed to freshen the team up.

The battered ones — Klein, Knott, Robinson and others — have been limited a little more in practice leading up to the trip to Norman to keep their bodies healthy. They’ve also been undergoing more treatment on the parts that give them trouble.

Mentally, Klein said it’s a new challenge every week preparing for a new team. But, physically, the grind is there.

“You’ve got to push it to the limits,” Klein said. “You’ve got to kind of ignore injuries and work through them, stay healthy as best you can.

“We’ve got to play the next six weeks and we don’t really get rest time.”