KNOXVILLE, Tenn. (AP) — After years of playing catch-up with the rest of the Southeastern Conference,Tennessee's defense finally is getting up to speed.

A variety of position switches and the infusion of a talented recruiting class have given Tennessee a faster defense, addressing what had been a major weakness and perhaps making the Volunteers less susceptible to the big play. Now the chief worries are a lack of experience and size.

The inexperience is most apparent. Defensive coordinator John Jancek said Thursday that the defense could end up playing 11-13 newcomers.

But the Vols also lack size up front as they attempt to replace all four starting linemen from last season. Over the last week, head coach Butch Jones has discussed the need to solidify the defensive tackle position as the Vols gear up for their Aug. 31 season opener against Utah State.

"It's a great concern," Jones said. "And we have to get some individuals to step up. ... We all know that you have to stop the run first. We are talented, but we are also very young. It is a concern moving forward."

Tennessee faces the task of replacing Pittsburgh Steelers sixth-round draft pick Daniel McCullers, who was listed at 351 pounds last season. On this year's team, the only healthy defensive lineman with a listed weight of 300 or above is 306-pound freshman Michael Sawyers.

In an effort to improve the line's athleticism, Tennessee moved Jordan Williams from end to tackle and shifted Curt Maggitt from linebacker to end. Maggitt was back at practice Thursday after missing nearly two weeks with an ankle injury. The change in emphasis should boost the pass rush of a Tennessee defense that had the fewest sacks in the SEC each of the last two years, but it also could make the Vols vulnerable against strong running attacks.

"We're definitely a lot more athletic, a lot of movement, a lot of good hand technique," Williams said. "We've definitely improved with that. We're a little bit undersized, but we're moving around a bit. It's good. We're definitely going to be making plays there."

Defensive line coach Steve Stripling has said he'd rather have athleticism than size from his tackles if he can't have both. He likes the potential of this group. The problem is that none of Tennessee's tackles have much of a track record.

Williams has started eight games over the last two seasons, but he's adjusting to a new position. Sophomore Danny O'Brien hasn't started a game yet. Junior Trevarris Saulsberry could provide depth, but he just aggravated a knee injury last week. Junior college transfer Owen Williams remains untested. Tennessee's lack of depth could create opportunities for freshmen Dimarya Mixon and Sawyers.

"Playing defensive tackle is the real world," Stripling sad. "You've got to take on those 300-pound tackles, so you've got to be physical and strong, and you've got to stay strong. You want as many of those guys to be able to play as possible. Obviously, we're looking for more depth.