University of Tennessee defensive linemen Jordan Williams (54) and Danny O'Brien (95) jog back toward their lines during practice at Haslam Field.

KNOXVILLE - Danny O'Brien and Jason Carr really have no choice in the matter.

Tennessee's freshman defensive tackles are going to have to be ready to play.

With Mo Couch indefinitely ineligible following last week's Yahoo! report that alleged he received improper extra benefits and Trevarris Saulsberry sidelined for up to six weeks with a knee injury suffered in Saturday's loss at second-ranked Oregon, the Volunteers will be forced to play the redshirted freshman O'Brien and the true freshman Carr behind starters Daniel McCullers and Daniel Hood.

Both played a handful in the second half against the Ducks, and they'll likely get plenty of work when Tennessee visits 19th-ranked Florida on Saturday.

"Those guys understand that it's a huge opportunity for them, and even though we're low on the inside, these guys have been playing real hard today," senior defensive end Corey Miller said following the Vols' Tuesday afternoon practice.

"They came out and practiced hard. Danny had a great day of practice, and Jason had a great day of practice, so I'm confident these guys will be able to come in there and hold it down.

"They know they've got to go. They have to. There's no ifs, ands or buts about it. They've got to go. We're going to need them."

Against Oregon's high offensive tempo, the Vols rotated continually along their defensive line, sometimes running in four new bodies in the middle of drives, to keep that unit fresh. Once Saulsberry went down late in the second quarter, O'Brien and Carr often were the tandem at the tackles.

The Gators have neither the same tempo nor skill on offense, but Gainesville's mid-September sun is sure to wear down the game's biggest bodies.

Once fifth and sixth in the pecking order at tackle, O'Brien and Carr are now third and fourth in line.

"They've worked extremely hard," coach Butch Jones said. "We have no choice. Jason Carr has to be able to give us valuable repetitions. Everyone has to elevate their game. Then you throw in the offensive line of Florida -- a very, very talented and very, very physical group. This is going to be a line-of-scrimmage game.

"Jason's being mentored by our older players, and it's a great opportunity for him along with everyone else."

Both young tackles were four-star recruits out of high school.

The 6-foot-2, 287-pound O'Brien was the nation's No. 161 overall player in the 2012 class out of Powers Catholic High School in Flint, Mich. He shunned the chance to stay close to home offered by Michigan and Michigan State for Tennessee. Alabama and Florida were also on his offer list.

Carr, a 6-5, 285-pounder from White Station in Memphis, was one of the bigger coups by Jones and his staff in the 2013 class, as the Vols fended off a January push from Alabama to hold onto him.

Jones has been hard on Carr throughout his brief career. He dubbed him "the softest player out of Memphis" during one practice last month.

"I've been really impressed with Jason Carr's approach to learning and then how he's done," Hood said Monday. "Very talented guy, young, just a lot of things to work on. It seems like every week [O'Brien] keeps improving on one thing at a time, so I think he's going to be able to play some valuable minutes for us and help us out a bunch."

While Tennessee must hope O'Brien, Carr and fourth-year junior Greg Clark can provide depth at tackle, the Vols also need starters McCullers and Hood to be more productive.

"All of us really have to share the burden to pick our play and pick up our intensity in practice," said Hood, a senior.

The freshmen, though, will be thrust into the fire of an SEC opener against a Florida offense that's averaged 192 yards rushing in its first two games.

"I feel like if they can come in and help big Daniel McCullers and help Dan Hood for even if it's a couple of snaps," Miller said, "we need anything we can get out of them, because we can't have those guys out there on the field for the entire game."

Contact Patrick Brown at pbrown@timesfreepress.com.