— ARLINGTON, Texas – The misery Oklahoma experienced Saturday night wasn’t scarring. It takes something unexpected to cause that kind of shock to the system.

Seeing Texas A&M quarterback Johnny Manziel run from end to end of Cowboys Stadium wasn’t stunning, considering the Sooners’ troubles stopping the run this season.

The 41-13 loss to the Aggies in the AT&T Cotton Bowl Classic was simply a final exam in a subject OU had been flunking throughout the second half of the season.

“We’ve got to make improvements in all areas, run defense, pass defense, pressures, whatever we’re doing,” OU coach Bob Stoops said. “But again, some of it, too, our players have got to make some improvements. We had guys in position a bunch of times today to make plays, and they didn’t make them. The schemes and that kind of stuff only goes so far. Bottom line, it comes down to when you get opportunities to execute, you got to execute.”

It was crystal clear Friday night that OU’s defensive line was overmatched by Texas A&M. Manziel had an endless amount of time to throw and holes big enough to drive a truck through. Defensive ends R.J. Washington and Chuka Ndulue and tackles David King, Casey Walker and Jamarkus McFarland didn’t get off blocks and never came close to collapsing the pocket.

It wasn’t an oddity.

OU had 25 sacks this season with defensive linemen registering just 15.5 of the them. More telling was the tackles for loss total. OU had 55 this season with defensive linemen grabbing 25 of them. The Sooners averaged 37.8 sacks per season and 102.2 tackles for loss per season from 2007-11.

Defensive coordinator Mike Stoops hinted at the problem in the days leading up to the Cotton Bowl. The Sooners lack a down lineman that’s a consistent playmaker.

“We’ve just been kind of a group up front. We haven’t had a Tommie Harris, a Dan Cody-type of player up front,” he said. “It’s probably why we’re not like we were in  some of the years we really excelled. Up front is a big part of the game.”

One of the calling cards of OU’s great defenses has been dominant defensive linemen. This season, the Sooners didn’t have a first-team All-Big 12 defensive lineman for the first time since 1999.

What should scare OU fans is that with the exception of Ndulue, the defensive linemen used most of the season were seniors. If OU had better options, they would have been on the field.

OU got away with it in the first half of the season. By November, teams figured out spreading out the Sooners and running the ball was something they couldn’t handle.

“People started picking up on what we were doing. I think one thing was when we first came into the season a lot of people weren’t ready for what we were running,” said safety Javon Harris, who had one of OU’s few Cotton Bowl highlights with a second quarter interception. “We ran a lot man (coverage). A lot of teams just spread us out. When we started facing running quarterbacks, you have to account for them … Once you start spreading out, there’s a lot of gaps open, a lot of lanes open.”

The Sooners have the offseason to try to correct the problem. Perhaps an influx of defensive talent will arrive next month on signing day.

If it doesn’t, OU’s defense will get exposed like it did throughout the final month of the regular season and Friday night.