Since fall camp, Tennessee football coach Phillip Fulmer has had Dan Williams and Demonte' Bolden's names on his lips.

The two underclassmen needed to step forward. They needed to develop a sense of urgency.

They had potential to be good players, and that potential should be harnessed now instead of later.

At least until last week's 33-7 victory over Marshall.

That's when Bolden and Williams took significant steps toward becoming solid contributors in what the Vols hope becomes more like their five-man defensive line rotation of old.

They'll be called on for the rest of the season, starting with Saturday's noon game (TV: ESPN) at Memphis (1-2).

The loss of Justin Harrell, a preseason All-SEC selection who underwent surgery last week to repair a ruptured biceps tendon, hit the Vols (3-1) hard.

"Without his presence out there, getting you fired up, knowing he's going to be out there to make some plays, it's going to be kind of frustrating knowing he's not going to be there," linebacker Ryan Karl said.

"But on the other hand we have a whole bunch of other guys like J.T. Mapu and all them that can go out there and fill his shoes. When you have depth at defensive tackle like we do, it's just something you have to get past."

Still, the loss was significant.

"When you lose that guy, you've got a big physical guy that might have been one of the best in the country," UT defensive coordinator John Chavis said. "We really felt if we were able to play he and Turk (McBride) inside, if our ends had come on early, we felt like we may have had the best pair in the country.

"Well that's gone. We can't worry about what's not there. What we've got to focus on is what we have and how we can make it work. I think we're well on our way to get it done."

Bolden, Williams and Mapu are helping Tennessee's defensive line in the post-Harrell era.

All three players saw significant time backing up starters McBride and Matt McGlothlin.

Bolden, a sophomore, had two tackles and Williams one.

Both players recorded sacks.

Mapu, who returned for his junior season after a two-year absence for a Mormon mission, got his most playing time to date.

"We had to play him," Chavis said. "He's getting there. I hate to put a percentage on it, but he's getting better every Saturday, and we're excited about that."

The 6-foot-6, 290-pound Bolden was excited by the opportunity for playing time.

When Harrell went down, Bolden said the volume was turned up on his coaches' message.

"It's my time to step up, quit lagging around, put some urgency in my step," said Bolden, who has played in every game this season except Florida. "When he (Harrell) went down, I seized it. I told (defensive line coach Dan) Brooks maybe I can help this team out."

Help is needed.

The Vols' run defense ranks 81st in the country, giving up an average of 148 yards a game.

Air Force's 281-yard performance is the outlier, and that happened with Harrell playing at tackle.

Just last week, Marshall rushed for 126 yards.

Even so, Saturday was a step in the right direction.

"We did some good things," Chavis said. "I'm not ever going to say I'm pleased. I'm happy with the effort. If they keep the effort where it is and keep approaching practice where it is, then we can get to where we want to be."