McCullers happens to be a 6-foot-6, 362-pound nose guard who routinely lines up opposite second-team center Crowder during drill work.
"Danny's a load now," Vol offensive line coach Sam Pittman said recently. "We were laughing the other day: We had a one-on-one drill, and Mack Crowder was over the top of him. It looked like a little kid against a big ol' man, and Mack's 285."
Crowder may be dwarfed by McCullers but he isn't intimidated by him. Still, he admits that challenging the biggest player in program history on the practice field each day has been a unique experience.
"It was like hitting a wall, basically," he said. "I fired off as hard as I could but he didn't move anywhere. Basically, you hope to move him off the ball at least one yard. If not that, you hope to stalemate him and make sure he doesn't get the tackle."
McCullers understands leverage, which enables him to exploit his size. That makes him even more of a load to try and block.
"He's a monster," Crowder said. "He's got about a hundred pounds on me, which is pretty hard to move. It's hard for any of our guys to move. But he's making us all better. You can't ask for anything else."
In addition to massive size, McCullers has surprising mobility.
"He was going against (first-team center) James Stone in the pass rush, and James was driving him off to the side," Crowder recalled. "He (McCullers) did a spin move back inside, and that kind of surprised everybody."
Although he's still figuring out how to manage McCullers, Crowder is having a good fall camp. He is Stone's chief backup now that junior Alex Bullard has been moved to tackle.
"There's definitely an opportunity there," said Crowder, who redshirted as a true freshman in 2011. "James is a great center and he's going to make it hard for anybody to step up. But me trying to push for the starting spot makes James better, knowing that he has somebody behind him that can play. There is an opportunity there but I'm going to have to get a lot better before I take James' spot."
Crowder already notices improvement in one critical area.
"Learning the offense," he said. "As the center, you've got to control everybody on the offensive line. Last year I struggled with that a little bit but I've gotten a lot better."
Pittman believes Crowder's determination will make him a quality player in time.
"He's got a big heart, a big desire to play the game," the O-line coach said. "He works his butt off all the time. He's not even the same kid he was in the spring, so we're real proud of the way he's developed."
After watching in 2011, Crowder is understandably eager to earn some playing time in 2012. That drive pushes him to go all-out in practice.
"Wanting to get in there and play makes you come to practice with the mentality that you're going to try to take that starting spot," he said. "Most of the time it won't happen that day but it definitely helps you get better to know that you're going to have a chance someday to play."
Crowder packed just 270 pounds on his 6-foot-2 frame when he enrolled one year ago. He has added 15 much-needed pounds since then.
"That's helped a lot," he said. "Most of the weight I've gained has been muscle. It definitely helps against the defensive linemen because they're all hefty guys."
One, in particular.