KNOXVILLE, Tenn. (AP) The biggest question facing Tennessee's defense is whether it can solve its riddle in the middle.

The Volunteers must find a middle linebacker to replace A.J. Johnson, who ranked as the second-leading tackler in school history before his college career ended abruptly last November amid a rape investigation. Defensive coordinator John Jancek has described the competition as ''wide open,'' and head coach Butch Jones listed six candidates for the job at the start of training camp.

''We all rotate and we get about equal reps, so it's still a pretty open competition,'' said redshirt freshman Dillon Bates, one of the contenders. ''We're still all fighting, we're still all competing, we're still all coaching each other up.''

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A potential position switch could move one candidate out of the mix. Sophomore Jakob Johnson, who isn't related to A.J., has worked out at tight end the last couple of days as the Vols ponder whether his permanent home's on offense or defense. Other contenders include redshirt freshman Gavin Bryant, junior Kenny Bynum, sophomore Colton Jumper and freshman Darrin Kirkland Jr.

''I'm looking for a leader,'' Jancek said. ''I'm looking for someone who has great command on the field, great knowledge of our system and what it is we want to do. That's a position of concern, as you guys know. We have a great group there competing extremely hard. We're just going to have to sort this thing out sooner rather than later.''

In some respects, referring to this as a middle linebacker competition isn't entirely accurate. Jones notes that Tennessee spends much of every game in a nickel formation with only two linebackers.

But even in those situations, the Vols would need to find a second linebacker to play alongside returning starter Jalen Reeves-Maybin. Although Curt Maggitt has a hybrid defensive end/linebacker role, he typically plays end when Tennessee's in the nickel.

''I think the kids have done a really good job as a position group,'' Jones said. ''There are a lot of individuals vying for playing time, and we want to play a lot of players. ... I've been pleased with the linebacker group as a whole.''

The state of Tennessee's defense represents a major change from the recent past, when the middle linebacker spot represented the one sure thing on a team otherwise facing uncertainty.

A.J. Johnson was a four-year starter whose 425 career tackles represent the second-highest total since the school started measuring the statistic in 1970. He had 101 tackles last season to tie Reeves-Maybin for the team lead despite being suspended for the final three games. After graduating in December, he was indicted on aggravated rape charges in February and has a Sept. 29 trial date.

Jakob Johnson started Tennessee's final two regular-season games at that spot last season before Bynum took over in the Vols' TaxSlayer Bowl victory over Iowa.

Bynum says he weighed about 245 pounds during the bowl game but has since gotten down to 230 with the intention of reaching 235 by the start of the season. Jones said ''you can tell a major difference'' in Bynum after the weight loss and cited the junior's improved confidence and quickness.

''I definitely feel a lot quicker on the field and a lot more agile, being able to keep up with backs,'' Bynum said.

NOTES: Wide receiver Von Pearson participated in his first practice session Saturday, one day after being reinstated to the team. Pearson's suspension was lifted after prosecutors declined to file charges against him in connection with a rape investigation in which police had named him as a suspect. ''I thought Von's recall and retention from the spring were very good,'' Jones said. ... Jones complimented the Vols' ''workmanlike approach'' at Saturday's practice, one day after he criticized the team for showing a lack of maturity at Friday's workout.