KNOXVILLE -- It's a challenging dilemma for Peter Sirmon.

The first-year University of Tennessee linebackers coach knows what's required to be a good linebacker after a four-year career at the position at Oregon and a seven-year NFL career with the Tennessee Titans. But the group he's coaching is essentially a mystery.

"We want to play the players based on their demonstrated ability," Sirmon said after a Volunteers practice this past week. "Without a good body of demonstrated ability, it's hard to say who's good. I think it's a fair assertion to say we've got some issues. But these guys care about football enough, and they're tough enough guys, so I think we'll be able to find the pieces to make this thing a good defense."

Linebackers Nick Reveiz and LaMarcus Thompson were the Vols' leading and fourth-leading tacklers last year, but both have moved on. Junior Herman Lathers, UT's most proven linebacker and leading returning tackler, fractured his ankle in a June workout and remains out indefinitely.

"You're not going to wholesale change on one guy," defensive coordinator Justin Wilcox said. "Obviously, Herman played a lot for us last year and he's a leader on our team. We're all sad to see him go down. We're going to support him and get him back as soon as we can, but we need the other guys to step up to the plate and carry the flag."

That leaves the Vols with a mix of unproven players.

"I don't know how that's all going to work," Sirmon said. "That's the evaluation process we're going through right now. Guys have got to stay healthy, continue to improve, show some toughness and work through some things. Usually by the end of these kinds of things, the decisions kind of make themselves because the guys play themselves in or out of opportunities to play."

The pre-camp depth chart listed John Propst as the starting middle linebacker, Daryl Vereen as the starter at Sam (strongside linebacker) and Austin Johnson at Will (weakside linebacker). Freshman A.J. Johnson and oft-injured junior Greg King are working at Will, and freshman Curt Maggitt, converted safety Dontavis Sapp and sophomore special-teamer Raiques Crump have worked at Sam.

The Vols coaches are looking at guys in different spots, except for Propst, who had 14 tackles in 11 games to make the All-SEC Freshman team despite his third-string status last year. The coaches have liked his intelligence, though he doesn't fit their ideal size for a linebacker. And head coach Derek Dooley said Saturday that the 6-foot, 225-pound Propst needs to be in the middle.

"Mainly, that's what his physical makeup keeps him at," Dooley said. "He's a smart guy, he's instinctive, but he doesn't have the range as some of the other guys. That's kind of his role, and we need him to stay at Mike and it gives us a little stability.

"Some guys, the Sam and the Will, you can really get caught up in space a lot, and so guys who play better tackle-to-tackle need to stay at Mike. And then Mike, you need to have somebody with a lot of command who's got a real good understanding of the defense. So it's two things going at once, and [Propst] fits both of those."

As Propst said, "Mike linebacker has got to be able to talk out there. I feel like I do a pretty good job with that -- communicating with everybody -- and I've just got to continue to get better at it. I'm not a huge talker off the field or in the locker room; I just kind of lead by example and that's what I try to do. If I need to stand up and say something, that's a little bit out of my comfort zone, but if it's best for the team, then I'll do it."

The Vols still have three more weeks before the opener to evaluate and discover ways to address their most glaring problem.

Dooley admitted Saturday that he sees depth and competition as positives at the linebacker position. The three big freshmen -- Maggitt (6-3, 215), A.J. Johnson (6-3, 245) and Christian Harris (6-2, 235) -- likely are the reason for the coach's optimism.

"I like those three youngsters because of the type of people they are, the type of character they have," Sirmon said. "Obviously they have some nice physical tools and those things that'll be good for them down in the future, but they still have a lot to learn. They've got to accepted on this team, and we're not going to give them anything. Everything they're going to earn."

UT's staff is confident, though, that Sirmon can handle the dilemma.

"Pete is a high-output, low-ego guy," Wilcox said. "He's played the position at the highest level, he's extremely smart, he's a great communicator, he can teach the game and he's a guy who works his butt off. That's what coaching is."