Coming off an abysmal debut season with the South Carolina Gamecocks in 1999 under Lou Holtz, current Texas Longhorns head coach Charlie Strong made a decision that would shape the rest of his football career by installing a 3-3-5 defense that eventually became his calling card and helped lead him to Austin.

Now, 16 years after that crucial moment, Strong may have to move away from that alignment a year after fielding the No. 78th-ranked rush defense in S&P+ that also finished in that same spot in average yards per carry allowed (4.51).

At the least, Strong knows that he has a problem.

“It eats at you because, I think we ended up giving up a lot of yards, but our guys on defense, from Coach [Vance] Bedford and all of them, they understand we need to improve there,” Strong said in June.

The reason that Strong originally adopted the 3-3-5 defense was in order to deal with the first wave of spread offenses that were coming into vogue at that time, including early versions of the Air Raid run by Hal Mumme at Kentucky.

As those offenses have matured over the last decade and a half, the purveyors of those systems have become more adept at rushing the football — even Texas Tech, which used to abandon the run for games at a time, ran for 283 yards at 5.75 yards per carry against Texas last year. The Cal Bear Raid offense went for 280 yards on 6.83 yards per carry to close the non-conference season.

So while the Longhorns head coach prefers to scheme to limit big plays in the passing game and force offenses to move the ball methodically down the field, Strong may increasingly recognize that he needs to adjust his scheme to better control the line of scrimmage and suit his personnel.

The other option is what often happened last season — opponents were able to consistently gain enough positive yardage with the run to avoid long down-and-distance situations that tend to end drives and the ‘Horns got worn down by long drives.

As, a result, Texas gave up 21 rushing touchdowns, many of them in the red zone, as one might expect.

Strong’s defense will have to improve the run despite losing three significant contributors along the defensive line — star defensive tackle Hassan Ridgeway, nose tackle Desmond Jackson, and defensive end Shiro Davis, in that order of importance.

As documented here extensively, the loss of Ridgeway is the biggest concern because he was one of the most disruptive players at the position nationally against the run and the pass.

However, losing Jackson was also significant since he was strong enough to hold up against double teams, not a strength of any of the three returning scholarship players at the position.

Now the ‘Horns will have to make strides in fundamentals despite the need to get contributions from several of the five freshmen defensive tackles now on campus.

“When you give up big runs, it's about gap control and getting off of blocks and making sure you come down and when you put an extra guy in the box, the front is slanted one way,” Strong said.

“It's all about control and guys getting off of blocks. We didn't do a good job of stopping the run and making a team one-dimensional, we never did that last year. Usually when a team is able to run the ball on you, they're being more physical than you and tougher. That's what we can't allow. We have to improve our run defense.”

Changing the scheme could help that — playing the 3-3-5 alignment that Strong prefers requires a nose tackle who can consistently battle double teams in order to keep offensive linemen from quickly getting to the second level to take out linebackers and a versatile defensive end who can play head up on an offensive tackle and control the line of scrimmage.

It’s possible that a player could emerge into that role, one that 270-pound Cedric Reed filled admirably in 2014, but senior Bryce Cottrell lacks ideal height and length and sophomore Charles Omenihu needs to make a big leap to approximate Reed’s contributions.

And there isn’t a consistent nose tackle, either, as junior Poona Ford is too small, senior Paul Boyette is better in a gap-penetrating role, and sophomore Chris Nelson is a wild card.

Eventually, 329-pound freshman Gerald Wilbon should be able to step up into that position, but he likely won’t be ready to play extended snaps this season despite his impressive lower-body strength and big leap as a senior.

Fortunately for the ‘Horns, he’s joined by 292-pound D’Andre Christmas, 335-pound Chris Daniels, and 318-pound Jordan Elliott.

“Their body, when you're talking about 300 pounders, that's what you want to see,” Strong said. “When you talk about big guys who can move and won't get pushed around and they have enough athletic ability where they can get off of blocks and go make plays.”

So the answer for Strong may be a move to a more traditional four-man front, though that also presents some challenges, as it would require the Fox end to hold up against the run from a three-point stance, something that the current starter at the position, junior Naashon Hughes, didn’t do well last season — he’s much more comfortable playing in space.

The emergence of Omenihu as a 270-pound defensive end capable of playing opposite Cottrell could be a big development, and senior Quincy Vasser, a junior college transfer who played sparingly last season, also had a good performance in the Orange and White game.

Since Omenihu was much lighter last season and Vasher wasn’t ready to play, Texas now has more credible options to run an even front, not to mention freshman Andrew Fitzgerald, Strong’s dark horse of the class.

Wait, there’s even sophomore Breckyn Hager, who will be an option this season at Fox end after moving from linebacker in order to help the pass rush. He had an excellent spring, too, but like so many other players, is young and largely unproven.

If he’s more stout against the run, it’s possible that he could overtake Hughes at Fox, which would be one development that could allow Strong to maintain the ability to disguise more looks by playing that position in a two-point stance.

Otherwise, moving to a 4-2 would probably make sense for the Texas head coach.

Such a front could also feature more slanting by defensive linemen to confuse opposing blocking schemes and limit the amount of time players like Boyette have to spend as a pure nose tackle, instead playing over a guard as a two technique, as outlined by Ian Boyd at Inside Texas. It would also limit the stunting from the linebackers to make up for the gap coverage lost by playing three down linemen.

The 3-3-5 defense got Strong this far, but he may have to abandon it in 2016 to match the strengths of his personnel and fix a significant issue left over from the young but ultimately disappointing 2015 defense.