After Georgia Tech lost six defensive starters — three on the defensive line — to graduation, many figured the defense would take a step back, particularly against the run.

For better or worse, the Yellow Jackets have met that expectation. Without Jeremiah Attaochu, Euclid Cummings and Emmanuel Dieke on the line — Attaochu was drafted in the second round, and the other two made NFL camps — Tech is giving up 5.39 yards per carry, 118th of 128 teams nationally. Last season, defensive coordinator Ted Roof’s first, the Jackets’ number was 3.57, 18th in the country, the lowest average since 2007.

“We’ve got to do a better job against the run,” coach Paul Johnson said.

North Carolina, Tech’s opponent Saturday evening, averages a pedestrian 3.97 yards per rush, but has run 71 times for 309 yards (4.35) in its past two games, against Virginia Tech and Notre Dame, two of the better run-defense outfits in the country. After an aggravating home loss to Duke on Saturday, the Jackets will attempt to secure another critical ACC Coastal Division victory at Kenan Stadium, which would be their sixth in a row over the Tar Heels. Tech’s ability to harness the Tar Heels’ running game, and in the process help determine the pace of play in this clash of up-tempo and clock-grinding offenses, will weigh significantly.

“I think everyone’s just ready to get back out there and get back on that train and get it going again,” defensive tackle Adam Gotsis said.

With his three stalwarts gone from the 2013 line, Roof has tried different players and combinations and is still looking for a solution. Gotsis, the lone returning starter on the line, and Shawn Green have played the majority of snaps on the interior. KeShun Freeman, Roderick Rook-Chungong, Tyler Stargel and Kyle Travis have started at end. None of the four played significantly or at all before this season.

Behind them, linebacker play has been inconsistent. Overall, the tackling has at times been deficient, assignments have not always been carried out and opposing lines and running backs have won their share of battles.

The Jackets have given up 10 run plays of 20 yards or more in 209 attempts this season, one more than they surrendered in 422 carries last season.

Against Duke, the Jackets repeatedly misplayed the Blue Devils’ zone-read plays by filling the wrong gaps, letting them pick up big gains and convert third downs. With little reason to put the ball in the air, the Blue Devils pounded out 242 yards on the ground, Duke’s second-highest rushing total in an ACC game in coach David Cutcliffe’s seven seasons.

“We misfit some things, missed a couple tackles,” Roof said. “It’s like we got 6-yarded to death.”

It wasn’t the first time this season that the option has crossed up the Jackets.

The season began with Wofford, a triple-option team, collecting 271 rushing yards on 47 carries, a 5.8 yards-per-carry average. Wofford’s rushing total was, in fact, one more yard than the Terriers gained against Western Carolina on Oct. 11. Late in the first half, Tech botched an option run play and gave up a 92-yard touchdown run, the longest run in Tech’s record books ever permitted on Grant Field.

After being held to 96 yards in the first half, Georgia Southern shredded the Jackets in the second half with its option attack. The Eagles piled up 187 rushing yards and scored touchdowns on four consecutive possessions to take a 38-35 fourth-quarter lead before Tech’s last-possession rally.

It is a peculiar development, as the Jackets defense faces its counterpart’s spread-option offense routinely in spring practice and the preseason, although Wofford, Georgia Southern and Duke’s formations, plays and personnel groupings differ from Tech’s.

Further, Tech has done its best run defending against teams that run pro-style offenses, Tulane and Virginia Tech, a combined 58 carries for 223 yards for a 3.84 yards-per-carry average. Johnson doesn’t see the defense having merely an option problem.

“I’d say it’d probably be accurate to say we’ve had trouble with teams whatever they did,” he said.

That said, Roof expected to see the Tar Heels try their hand at zone-read plays with quarterback Marquise Williams.

“Absolutely,” he said. “They’ve got it in their offense. They have those plays, so, yeah. You’ve got to get that stuff corrected, because once you put it on tape, it’s out there for everybody to see. That’s our job as coaches and our players’ jobs to make those corrections and move forward.”