LSU was finally on the move.

After three short, fruitless drives that all ended in punts, the Tigers had strung a few first downs together. Leonard Fournette, who had been bottled up for most of the night, rumbled into the red zone as LSU sought to whack away at Arkansas’ 14-0 lead.

Two plays later, the Razorbacks sacked sophomore quarterback Brandon Harris on third-and-25.

That’s just one example of a disturbing trend that has plagued No. 17 LSU (7-2, 4-2 Southeastern Conference) during its consecutive losses to Alabama and Arkansas. The Tigers have frequently found themselves behind the chains, doomed to nearly unconvertable third-and-long situations because of negative plays on first and second downs.

“Every drive it was something,” said senior right tackle Vadal Alexander, whose 15-yard facemask penalty moved the offense back to the 45-yard line after Fournette entered the red zone. “Penalties, turnovers, sacks. When that happens to an offense, it’s hard to be successful on third-and-15, third-and-10.”

Third-and-long has almost become the norm for LSU over the past two weeks. The Tigers needed to gain 10 yards or more on 12 of their 25 third downs against the Tide and Razorbacks. Staying ahead of the sticks will be at a premium when LSU takes on Ole Miss’ talent-laden defensive front at 2:30 p.m. Saturday in Oxford, Mississippi.

Junior defensive tackle Robert Nkemdiche, the consensus No. 1 overall prospect in the 2013 class, anchors a unit littered with former four- and five-star prospects.

“Their whole defensive line is quick off the ball. They get off the ball as pass rushers,” redshirt freshman offensive guard Will Clapp said. “They’re a different front. All their defensive linemen are athletic up front and get after the quarterback.”

No. 25 Ole Miss (7-3, 4-2) averages 1.8 sacks per game, but its defense causes far more problems for running backs than quarterbacks. The Rebels pile up almost eight tackles for loss per game, an area of concern for the Tigers during their two-game skid.

Alabama and Arkansas brought down LSU’s running backs behind the line of scrimmage seven and eight times, respectively, leading to those problematic third-and-long situations. The Tigers also struggled to keep opposing defenders out of the backfield on passing plays, most notably while giving up five sacks against the Razorbacks.

“We got pushed back in the pocket on a few plays,” Clapp said.

Those negative plays almost always resulted in unmanageable third downs. LSU’s average third-down distance in the last two games was a staggering 9.7 yards, and it converted only 36 percent (9-of-25) of those.

Six of the nine conversions occurred when the Tigers needed five yards or less. They went only 3-of-17 on third downs of 8 yards or longer. In light of its average third-down distance of 7.9 yards and 44.4 percent conversion rate during its 7-0 start, consistent third-and longs have become a severe issue for LSU’s offense.

“We continually put ourselves in third-down-and-long situations,” coach Les Miles said Monday. “When you do that, you tell that defense to come get you, and they did. They obliged us.”

Boy, did they. Arkansas picked up two sacks on third down, one of which followed Alexander’s facemask penalty to put LSU in fourth-and-35. Over the past two games, the Tigers have lost yards on eight second- or third-and-long plays.

Penalties have also contributed to LSU’s unfavorable down-and-distances, such as Clapp’s false start that turned a third-and-7 into a third-and-12 with his team down 10 against the Razorbacks. Harris threw an 8-yard completion on the ensuing play.

“We’re putting ourselves in situations we wouldn’t be in if it wasn’t for silly penalties that we could fix mentally,” sophomore receiver Malachi Dupre said after the loss to Arkansas. “You take those away, and we don’t have to call certain plays that are more difficult than others and aren’t hard to execute.”

LSU’s third-and-long problem actually starts on first down, where run-first teams typically need to thrive. The Tigers faced second-and-10 or longer five times at Alabama and eight times against Arkansas. Their average second-down distance on non-goal-line situations between both games was 9.05 yards, forcing Miles to more frequently rely on the now-struggling passing game on early downs.

LSU even ran some hurry-up while trying to overcome a 21-0 deficit last Saturday, an uncommon wrinkle in Miles’ system.

“I didn’t enjoy it at all,” he said after the game. “I would rather be up 10 points trying to run it out.”

The upswing in third-and-long situations has coincided with a decrease in points (30 combined) and rushing yards (122 combined), two statistical categories LSU excelled in during its unbeaten start. Alexander said staying ahead of the chains is a matter of being more efficient on first down.

To do that, he said, the Tigers must have a “workman’s mentality” like they had back in fall camp.

“We’ve got to be more crisp and clean. Everything has to be more smooth on first and second down,” Alexander said. “Forget all the noise and all the mistakes you made in the past. Just get back and go to work, that’s the only way you’re going to fix things.”

BEHIND THE CHAINS

LSU’s third-down conversions in losses to Alabama and Arkansas

Thrid down distance: third down conversions

5 yards or less: 6-of-8 (75.0 percent)

8 yards or more: 3-of-17 (17.6 percent)

Follow Marcus on Twitter at @RodrigueAdv.