In spring training, fully healed from his ankle woes, Defensive Coordinator Tyrone Nix asked the talented rising sophomore to concentrate solely on middle linebacker.
D.T. obliged, soaking in everything he could, from Nix and Cornell, about middle.
Apparently, however, Nix has more in store for D.T. when fall ball rolls around.
"We are in the process now of me learning multiple positions and different things," said D.T. "Coach Nix has stressed to me to know everything there is to know about middle and outside linebacker.
"Knowing middle LB helps with the transition to OLB. Middle LBs have to know what the OLBs are supposed to do in order to direct them and guide them, so it shouldn't be hard for me to adjust to more than one position when I'm called on."
In the offseason, D.T. has been a diligent student of the game.
"I've worked hard on recognizing offensive sets and knowing what they are going to do before they do it," he said. "I played a lot last year on instinct while I was learning. I have to keep learning from guys like Cornell and Coach Nix.
"I was not patient last year. I wanted to see something and go, but you have to have more control and discipline. I gave the effort, but I wasn't specific enough in what I was supposed to do. I was attacking with my eyes closed, so to speak."
Cornell has been a tremendous influence on Shackelford, and D.T. is quick to give him credit.
"Jonathan has done a lot for me. He's very smart and it's not just about football. He tells me all the time it's important how you carry yourself off the field and in the classroom. There's a correlation to how you carry yourself on the field," explained D.T. "He's been very willing to tutor me and teach me. I'm fighting him for his job and he still helps me all he can. He's not selfish at all. He's a great example for me, on and off the field.
"We respect each other and that will help make us a better football team, no matter who is out there playing."
Shackelford, who now weighs 238 pounds and bench pressed 410 pounds in the spring offseason program, is putting in extra time in the summer offseason.
"Guys like H.R. Greer and Joel Kight, to name a couple, really push me to work harder and I push them too," he noted. "We've got a good chemistry and work ethic going. We work beyond what is required in the summer and it will pay off."
D.T. is very excited about having a veteran defensive line to play behind this fall.
"As a linebacker, you are not going to make as many plays if your DL is not strong. We don't have to worry about that this year," Shackelford stated. "Guys like Ted Laurent, Jerrell Powe, Lawon Scott - all those guys are as good as everyone thinks they are.
"Not only that, but they are leaders of the team as well. Big Powe having team cookouts and Lawon looking out for the younger players, and so on. It's cool to watch them work on and off the field as leaders. Those guys influence the younger guys in so many ways, and it's all good."
D.T. said he's not just excited about the Rebel defense, he's seeing sparks from the offense in 7-on-7 volunteer drills.
"They are making plays and getting better and that's what we need from them. I like the way they work and I like what I see in their development," he closed.
#42 will be a staple in the Rebel defense in the fall.
And it may not be just as MLB.