Christian LaCouture and Quentin Thomas lay on the field writhing in pain.

LSU trainers rushed to the sides of the Tigers’ defensive tackles as a sparse crowd remaining in Tigers Stadium rumbled with concern.

They ought to be.

Mississippi State’s 34-29 win over LSU on Saturday night exposed what appears to be a crippling weakness for coach Les Miles’ bunch: a soft spot up the middle.

So having your two starters at tackle collapse on one play was a mouth-gaping moment for many. Thomas, playing with a torn biceps in his right arm, injured his left arm, and his status is unclear. LaCouture “should be fine,” Miles said after the game.

Still, there’s concern for the depth, experience and capability of the center of the Tigers’ defense.

The Bulldogs ran for 310 yards between the tackles against LSU, according to ESPN stats. They ripped off runs of 56 and 66 yards on running plays up the gut, and many of State quarterback Dak Prescott’s 105 yards rushing came at the heart of LSU’s defense.

“We just need to focus on some things,” LaCouture said after the loss, just the eighth home loss in 10 years for the Tigers. “We had a couple of miscues. There were just a couple of things they gassed us on tonight.”

LSU (3-1, 0-1 Southeastern Conference) tumbled nine spots to No. 17 in The Associated Press poll Sunday, the biggest fall in 10 years in those rankings. Meanwhile, players were expected to watch a gruesome replay of the game Sunday.

“We need to look at the film and see how to improve on that,” LaCouture said.

This team entered the season with a handful of concerns and question marks. The Tigers had to replace a starting quarterback, running back and one of the best receiver duos in school history.

Those worries — not settled, mind you — overshadowed this: replacing two defensive tackles in Ego Ferguson and Anthony Johnson. Ferguson, a third-round NFL draft pick, left after his redshirt sophomore season. A former five-star recruit, Johnson, a junior, went undrafted.

Oh, the woes of early departures. It hurt LSU at defensive tackles the season before, too. Bennie Logan left after his junior season in 2012.

These early departures force the Tigers to thrust young and inexperienced players into key roles, and they’ve hurt the depth at the position. True freshman Davon Godchaux is playing several snaps a game, and the Tigers appear to have just a three-man rotation at tackle: LaCouture, Thomas and Godchaux.

What’s confounding: three redshirt freshmen defensive tackles are rarely seeing the field.

Frank Herron and Greg Gilmore didn’t play against Mississippi State and Wisconsin, the Tigers’ two competitive games this season. Maquedius Bain is seeing minimal time in the rotation, but much of it is coming late in games.

Herron and Gilmore, part of the 2013 signing class, were four-star guys ranked in top 10 at their positions out of high school. Bain was rated four stars, too.

Asked about Herron earlier this season, Miles suggested that he was not prepared enough to play against the Badgers.

Miles touted Herron during fall camp, calling him “a beast.” Defensive coordinator John Chavis seemed excited about the prospect of the Tigers’ depth up the middle.

“We like to have at least five (players), and we feel better when we’ve got six that can play. We like to rotate them,” Chavis said after the first week of preseason practice. “We like to get those guys some playing time. We’ll do the same this year. We’ll play at least five, possibly six, defensive tackles.”

A month into the season, just three seem to have rotated for significant playing time. LSU’s situation at defensive tackle is in such a place that Thomas is fighting through a torn biceps to not just play, but start.

Meanwhile, the Tigers moved Lewis Neal, at 255 pounds, from defensive end to tackle. He plays in spots.

Defensive tackles aren’t the only ones to blame. Many times, linebackers were absent when Prescott or a running back reached the second level, something that unfolded in the second half against Wisconsin too.

Either way, LSU must find a fix for its sore spot. The Tigers play five teams in the top 40 in rushing offense in the nation in their final eight games.

“There’ll be changes made,” Miles said after the game referencing no specific area.

Follow Ross Dellenger on Twitter @DellengerAdv. For more coverage of LSU football, follow our Tiger Tracks blog at http://blogs.theadvocate.com/tigertracks/.