Georgia Tech lost only three starters from its 2016 defense — linebacker P.J. Davis, defensive tackle Patrick Gamble and defensive end Roderick Rook-Chungong. Gamble’s graduation, in particular, left a rather gaping hole.

In two years as a starter, Gamble gave the Yellow Jackets rugged play and leadership, putting together enough of a career that he should get a chance to play in the NFL. This spring, those toiling to follow Gamble and another graduating defensive tackle, Francis Kallon, won’t have much experience to rely upon to accomplish the task.

“We’re really, really unproven inside on defense,” defensive coordinator Ted Roof said. “Really, really unproven.”

The group of five scholarship defensive tackles under defensive line coach Mike Pelton’s supervision is among the least experienced at that position in coach Paul Johnson’s tenure. In 19 career games and 10 starts, Kyle Cerge-Henderson has made 38 tackles in his career, making him the relative veteran. The other three who have played, Brandon Adams, Desmond Branch and Brentavious Glanton, were first-year players last season and had a total of 17 tackles. The fifth returnee is Chris Martin, who redshirted.

“Inside’s where we lost the guys, so we’ve got to find somebody,” Johnson said last week.

Pelton has a hefty task in front of him. Even with Gamble doing the job in the middle last season (54 tackles, team-high 10.5 tackles for loss), Tech ranked 13th in the ACC in defensive yards-per-carry (4.73). It was the seventh time in Johnson’s nine seasons that the Jackets have been eighth or lower in that statistic.

Other units around the defense look strong — particularly the secondary, where all five starters return — but, as coaches are wont to say, it starts up front.

“Just trying to work guys, just trying to figure out who’s what,” Pelton said. “They’re working.”

At 6-foot-1 and 295 pounds, Cerge-Henderson is toward the bigger end in the group, but has work to do. To become more effective, he needs to continue to grow stronger and more explosive, capable of disengaging from blocks and holding the point in the running game.

Cerge-Henderson, a junior, was expected to redshirt in 2015 before injuries put him on the field midway through the season. He said he wanted to use the spring to be better with his hands in the pass rush.

“I’m already more of a run stopper, but I want to develop my game into more of a pass rusher, so using my hands instead of just trying to bull rush everybody, because this is college and this is the ACC,” he said.

Branch, a junior who transferred from a Texas junior college last year, and Adams and Glanton, both sophomores, played smaller roles last season. Martin is trying to catch up with them.

Adams, who played in short-yardage situations as a freshman, has caught coaches' attention in the first third of spring practice — Tech had its sixth of 15 practices on Wednesday — having lost weight to allow him to be more active and productive. Pelton and Roof are hopeful that Adams, who is around 335 pounds, can be condtioned enough to be a part of the rotation if he can continue to lose weight.

Branch played an increasing amount over the course of the season, moving from end to the interior. As a converted end, he is a little quicker and more athletic than his counterparts.

“Desmond is an excellent pass rusher, so I think he really helps us in that aspect,” Cerge-Henderson said. “He’s also becoming a run stopper, as well. I’m teaching him certain things when it comes to how to stop the run, and he’s teaching me things on how to pass rush.”

Pelton has challenged Glanton, who played in six games last season, to demonstrate more urgency and improvement before the spring ends.

They’ll be joined by incoming freshman Cortez Alston and possibly Antwan Owens, who could play either end or tackle.

Out of the five returnees and the one or two freshmen, a rotation of four capable tackles going into the season would be a success for Tech. Pelton would have time to develop it, also. None of the seven will be a senior in the coming season. Roof does like that the five are relatively similar in their development.

“It’s good to mix it up, shake it up and see how people do, see how they compete,” Roof said.