KNOXVILLE - Danny O'Brien was once in the same shoes Kahlil McKenzie and Shy Tuttle now find themselves wearing.
Granted, those cleats were much smaller.
Tennessee is a week into preseason camp, where the Volunteers are trying to prepare McKenzie and Tuttle, touted recruits-turned-freshmen defensive tackles, to be ready to make meaningful contributions right away.
O'Brien, now a fourth-year junior, was once a freshman defensive tackle, too, though he was afforded the luxury of a redshirt year.
"I'm sure what Kahlil and Shy are going through is a little bit harder, because when I was a freshman we didn't have to emphasize too much running down the field after the ball," O'Brien said after Saturday afternoon's first practice in full pads.
Shy Tuttle entered his first preseason camp with the Tennessee Volunteers with an edge over most freshmen, thanks to his participation in spring practice after enrolling early."Just picking up everything, it's the little stuff that people don't really know. It's the small calls, the words we're hearing from the back end and being able to pick up stuff like that. It's really just our football intelligence - we call that F.B.I. - and understanding the game. Why does an offense do this? And what can come out of that? The physicality part, we're getting there."
That's the part of the game Tuttle and McKenzie probably have down already, given how massive both newcomers are.
McKenzie is 6-foot-3 and around 330 pounds, with legs that more resemble the trunks of two sequoia trees.
Tuttle, who enrolled at Tennessee in January and went through spring practice, is 6-3, 315.
Both committed and joined the Vols amid considerable hype, mostly because it's been a long time since Tennessee landed such highly-rated players at defensive tackle. The hype certainly wasn't slowed when McKenzie and Tuttle impressed in a one-on-one pass-rushing drill during practice Thursday.
Tuttle drove Marcus Jackson, Tennessee's starting guard and a fifth-year senior, into the backfield and eventually into the ground before his defensive teammates mobbed him in excitement.
Then McKenzie bowled over Austin Sanders in a sheer exercise of power.
"Obviously Kahlil's got great size," defensive coordinator John Jancek said after that practice. "He's shown some power. He's got to practice on a more consistent basis. Kahlil's a great kid, and I do like him at this point. He's a true freshman, so he's got a lot to learn."
Saturday was head coach Butch Jones's turn to pump the brakes on the two freshmen.
"We have some youngsters that are very, very talented, but they are learning to play at a high level of collegiate football," he said after Saturday's practice. "I've said it: We have to be very, very cautious that we don't place too many expectations on 17- to 18-year-old kids being in a college football program for the first time playing in the Southeastern Conference.
"I think a lot of times we look at the (recruiting) rankings and think that you just all of the sudden fix everything. They're just like our kids. They grow, they develop, they mature at a different pace. We're going to be patient with them. Every day is a learning experience for them. They're doing a good job with it, but we're in no way or shape ready for games yet, and we don't need to be."
Jones called defensive tackle an area of concern for the Vols at this point. O'Brien and second-year junior college transfer Owen Williams are the only returning players with any experience.
O'Brien welcomes the additions.
Along with O'Brien - the 6-2, 286-pound former four-star recruit - graduated seniors Jordan Williams and Owen Williams hogged just about all of the playing time in 2014, which led to some gaudy snap counts and all three playing through various injuries.
Owen Williams broke his thumb early in the season. Jordan Williams broke his hand in October. O'Brien missed spring practice because he required surgery in the winter.
So while he's willing to play as many snaps as Tennessee needs, O'Brien understands the benefits that come with the addition of McKenzie and Tuttle and the emergence of Kendal Vickers, a redshirt sophomore.
"It's great, and that's how you build championship programs," O'Brien said. "That's why Coach Jones recruits those big-time guys. It really helps me as a leader because I can't slack off and I can't show weakness. They're looking and modeling what they've got to do and their mental toughness and all that kind of stuff, and they're looking at me for that.
"It makes me a lot better player. I know I've got them on my heels, and we're going to compete all the time, just like we compete all the time."
Contact Patrick Brown at pbrown@timesfreepress.com.