LATROBE, Pa. -- Twenty yards away, Mike Tomlin was watching another drill when a commotion behind his back caught his attention the other day.
"Big Dan!" the coach bellowed.
During 1-on-1 blocking drills, Dan McCullers had knocked the helmet clean off Larson Graham. And then, quite deliberately, Big Dan -- all 6-foot-7 and 352 pounds of him -- fell on top of the offensive lineman, driving the first-year tackle into the ground. Bug, meet windshield.
A day later, McCullers was at it again, this time dislodging the helmet of center Parker Collins as a brief scrum ensued with Big Dan throwing a couple haymakers.
For the record, Tomlin detests in-team fighting. He sees it as a waste of valuable practice time and a potential cause of unnecessary injury. But here's thinking that, deep down, Tomlin might have enjoyed this one just a little.
It was a rare flash of emotion -- of any kind -- from McCullers, the fourth-year tackle, who intrigues with his gargantuan size, but confounds with his inability to use it consistently. Obviously, McCullers is well aware of his reputation as a gentle giant, but he doesn't care for the label.
"They can say what they want to say," McCullers was telling me at Saint Vincent College. "I know what I can do on a football field. I don't have to go out there and be enraged to be a dominant player. I know what I can do. Go hard and stay mentally in it, and I'll be all right."
This training camp, as in the last few camps, McCullers is in for a fight to earn a roster spot. He's made just two career starts and was a game-day inactive nine times last season, appearing in a career-low five games.
While Leonard Fournette and the Jacksonville Jaguars gouged the Steelers defense for 45 points and 164 combined rushing yards, McCullers watched from the sidelines in sweats. But he wonders if things may have been different had he played.
"I think about it a lot," McCullers, who played in all 16 games and had a career-high 17 tackles and one full sack two years ago, was telling me. "Not being able to play that game, just out there watching and seeing that they were able to run the ball, I felt like I could have helped with that game.
"We've got (Jacksonville) again this year. If I'm on the team, hopefully I'll play that game and help stop the run."
But McCullers' job is also on the line for reasons out of his control. He was drafted in the sixth round in 2014 as a pure run-stopping nose tackle. However, that position is going the way of the fullback and kickoff returner as the game is increasingly pass-centric.
As we've seen during this camp, the Steelers are evolving further and further away from their traditional 3-4 base, and moving more toward hybrid schemes with six and even seven defensive backs on the field. Technically, Javon Hargrave is the starting nose tackle, but he has the athleticism to play any position on the line. Hargrave played in 47 percent of all defensive snaps last season.
McCullers' real competition this camp is L.T. Walton, Joshua Frazier, Lavon Hooks and Casey Sayles. Leading that group is new defensive line coach Karl Dunbar, who replaces John Mitchell, the long-time D-line coach whose title now just reads "assistant head coach."
Dunbar's resume includes a dozen years experience in the NFL and, let's just say, he's a lot less vocal than Mitchell. That's probably not a bad thing for McCullers, who at times seemed to be a favorite target of Dunbar's predecessor.
"He's a younger guy, he's well connected with Mitch because he played here back in the day," McCullers said of Dunbar, an eighth round pick of Pittsburgh's in 1990. "Dunbar's been working with me, he likes me. We'll see what we can do.
"It's a little different, not as hard-nosed. He doesn't go at you verbally. He's a more laid back type."
McCullers says he's already starting to see the results of working with Dunbar. Whether that will be enough to retain his roster spot remains to be seen.