He can't hide a smile when recalling his upbringing in Decatur, Ala. His parents, Malcolm and Sherry, taught him the value of hard work. They were, and continue to be, disciplinarians. Malcolm is self employed. Sherry is a hair dresser.
"They've always pushed me," Shackelford said. "I don't have the richest parents in the world. It's not like I was raised up in a family of millionaires. They just made sure they taught me the values and qualities that you've got to have to be a good person."
There was a strict academic code in the Shackelford house. D.T. had to make good grades. Any grade below an A or a B was unacceptable. So even though he was making a name for himself on the football field as a standout linebacker for Austin High School, he was keenly aware education came first. Football was always secondary.
Shackelford, a Liberal Arts major, is entering his junior year at Ole Miss. But he still gets regular calls from his parents. Where he stands academically is usually one of the first questions asked. The standard has never changed, no matter how old he gets.
Because grades matter. How he carries himself matters. Hard work matters.
"Nobody can take that piece of paper, that diploma, away from you," Shackelford said.
So he makes sacrifices. Some weekends, he'll replace a night out with friends with a night spent in the the gym. Or at home studying. He often recruits teammates to do the same. It is all a part of his maturation process, his growth.
"If you don't work hard, you won't go to the next level," he said. "It's that simple. We try to complicate things so much. It's just simple. Hard work equals success. If you don't (work hard) don't expect to go far. You won't."
Ole Miss was a disappointing 4-8 overall and 1-7 in Southeastern Conference games last season. Shackelford was a recurring quote in postgame interviews. He was frustrated, and vocal in his disappointment. The sting only intensified with each loss.
The year brought back difficult memories of high school. Austin never won more than five games in any of Shackelford's four seasons, though it did make the playoffs -- but was eliminated in the first round -- his senior year.
"It was kind of like I was reliving it, because in high school we had the same thing," he said. "We had all the talent. We had a good coaching staff. But when we got on the field, we couldn't put it all together. It gets really frustrating because you're putting your all into it and not getting the results you want."
Shackelford emerged as a leader as a sophomore. He had to, not that it was new to him. The 6-foot-1, 235-pound Shackelford learned the ways of leading as a Command Sergeant Major in the Austin High School JROTC.
"I wasn't trying to mess with ROTC," Shackelford said. "The first thing I'm thinking is he's trying to put me in the army. But he was telling me it wouldn't qualify you to be in the army, just that it teaches you a lot of stuff."
And it did. Soon enough, he was put in charge of a battalion consisting of classmates. Shackelford always believed he had leadership ability but Colonel Walker and the JROTC, he said, developed it. He was humbled. He had to be an example as an appointed officer, as a star football player and as a student.
"Once people see you being a leader, you don't want to be hypocritical. You don't want them seeing you doing right on the football field but doing something wrong in the classroom. They go hand-in-hand," he said.
"All kinds of stuff comes into play when you talk about being a leader. Some guys have it. Some guys develop it over a certain period of time until you start filling that role. After a while, you don't want to let nobody down. You want to make sure you're doing the right things and not leading anybody down the wrong road."
JROTC was similar to football and to his home life. Yes, he had to answer to someone else, but there was the expectation of personal accountability.
"It humbled me a whole lot," Shackelford said. "When the colonel or instructor tells you to do something, you do it. There's no back-talk. If you're told to run a mile, you run a mile. And it's the same thing in football. No matter how far up you go, you're always going to have somebody to answer to. You always will. That's one of the biggest things (ROTC) taught me. You have to humble yourself because if you don't, somebody else will."
As will 4-8 seasons.
Shackelford said last season's misfortunes somewhat stemmed from a lack of personal accountability throughout the team. A couple of players were dismissed for a violation of team rules. Others maybe weren't doing their part in the weight room or in practices.
Shackelford won't name names. It is not his style. He simply acknowledged a renewed work ethic this offseason in the team's strength and conditioning program. Ole Miss opens spring practices March 28.
"I see a big improvement in our work ethic. I feel like everybody wants it more. As a team, collectively, we got together and felt like either all of us were going to be all in, or some people are going to leave. We gotta make sure we have a group of guys that's willing to sell out to Ole Miss football."
Shackelford has always been focused on winning. And improving. And leading by example. Sure, he intends to be vocal in the spring, but only when the situation calls for it. He wants his teammates to follow his lead in the work he puts in, in his dedication.
"I feel like I am (a leader)," he said. "Not in a cocky way, still being humble. At the same time, I recognize I do have a big role on this team, and I know that players will follow me. If you don't have good leaders, you're really not going to have a good team."
"D.T.'s becoming more disciplined in the fundamentals, which is what he needs to do," Ole Miss defensive coordinator Tyrone Nix said. "He's seen the system work, and he knows if you do the little things, you're fundamentally sound and disciplined, we'll be a better unit. D.T. realizes now that he needs to take on a bigger leadership role, and he appears ready to do so."
He'll again wear many hats for Ole Miss defensively. He is currently slotted as the starter at weakside linebacker, with sophomore Mike Marry No. 1 at middle linebacker in place of longtime starter Jonathan Cornell, who graduated.
The Rebels were decimated by injury last season, pushing Shackelford to defensive end on occasion. He collected 48 total tackles -- good for seventh on the team -- nine tackles for loss, five sacks and one fumble recovery.
"We got what it takes. We really do," he said. "We lost a lot of people, but at the same time, we've got what it takes. Like with any team, you have to have guys step in and fill their shoes. You're going to always have people that doubt you. That's life. It don't matter what it is. You have to outwork them and show them on the field. You have to be about it."
Follow the leader.