UT defensive coordinator John Jancek, left, listens to Butch Jones during a game against Arkansas State at Neyland Stadium in this 2014 file photo.

KNOXVILLE -- As he watched his defense work and perform during 14 practices the past five weeks, Tennessee defensive coordinator John Jancek continually had to remind himself what was missing.

The Volunteers operated without about half of their starting defense this spring as offseason surgeries and other injuries took their toll on some players, particularly on the defensive line.

As the spring concludes with Saturday's Orange and White game, Jancek remains cautiously optimistic that Tennessee can be pretty good on defense in 2015 after returning most of an improved unit from last season.

"You know I would never admit to anything like that even if I felt that way," he said with a smile after Thursday's practice. "I think we've got a chance. I think we've got a good group coming back. We're going to have to stay healthy, certainly.

"We're going to have to work hard over the summer. We're going to have to work hard throughout camp. We've got a lot of things that we need to continue to improve on."

Jancek's defense certainly has some building blocks at each level.

Derek Barnett and Curt Maggitt proved to be one of the SEC's best pass-rushing duos last season. Jalen Reeves-Maybin could be poised for an All-SEC season at linebacker. Cam Sutton and Brian Randolph headline a secondary that blends a veteran presence with young talent.

The Vols have recruited more talent and more speed on defense, but it'll be dependent on some freshmen. Shy Tuttle and Kahlil McKenzie will need to help at defensive tackle. It's wide open exiting spring at middle linebacker, where Darrin Kirkland could be a potential starter after missing the spring.

"There's going to be a lot of young guys in there intermixed, and that's just the process we're having to go through," Jancek said. "It's going to be fun. It's going to be challenging for us as coaches and as players and as a team.

"That's why you do it, though. That's what motivates us as a coaches, to find ways to get the job done, even when we have some young players. That'll be a challenge for us."

Blair's big summer

Dontavius Blair, the touted junior college transfer who redshirted last season, may be Tennessee's most gifted and imposing offensive tackle, but he's remained with the second-team offense all spring.

There have been encouraging signs of progress recently for the 6-foot-8, 300-pounder, though, and offensive line coach Don Mahoney is proud of how hard Blair has worked to prove himself to his teammates.

"He doesn't want to let the guys down in the room," Mahoney said. "He definitely doesn't want to let Vol Nation down as well. I think his attitude (is good) in terms of knowing that now is the time.

"I believe he's going to have a tremendous summer. I really do. That's why I feel encouraged the way he's leaving spring right now that he's going to provide us with the help we need this fall.

"How soon it will come, we'll talk more once fall camp hits after a few practices, but I like where his mind's at as far as attacking this thing and getting better."

Mahoney talks Mosley

While he recovered from a broken leg last season, redshirting freshman Charles Mosley often shadowed Tennessee's offensive linemen in practices and meetings, but he began spring practice on defense.

Mosley was back with the offense, albeit in a orange defensive jersey, for a second practice Thursday.

"For him to get some reps at the spot in just a quick period of time, it was good to see that there's some things he had a lot of recall," Mahoney said. "That was encouraging. He's such a big, powerful, athletic -- all the things we felt coming into the recruiting of him -- he certainly showed that.

"The most encouraging thing was his overall body language and his demeanor and the way he attacked it. He's got a tremendous attitude. He wants to play whatever. He wants to win."

Mosley's long-term future likely won't be determined until August training camp.

"That's Coach Jones's call," Mahoney said. "I will do everything I can to recruit him as an offensive lineman. ... He really can't go back and forth. He needs to focus in on one thing."

Confident coordinator

Offensive coordinator Mike DeBord was pleased with how Tennessee's up-and-down passing game showed signs of improvement during the final week of spring practice.

He already felt confident in a ground game spearheaded by a dynamic trio of quarterback Josh Dobbs and running backs Jalen Hurd and Alvin Kamara.

"I think it can be really good," he said. "I feel like our offensive line's really improved, and our running backs ran the ball well this spring. I feel good with the running game."

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