With Allen sidelined, sophomores Inky Johnson and Roshaun Fellows are the obvious choices to fill the cornerback spot opposite Jonathan Wade.
"Inky Johnson went in Saturday (after Allen was hurt) and did a good job," Fulmer noted. "And Roshaun Fellows started there (corner) at the beginning of the year."
As much as Allen's talent will be missed, his leadership could be missed even more.
"It's always very difficult to replace one of the best players on your team," Fulmer said. "We'll miss his energy and enthusiasm on defense. We'll miss him on special teams and we'll miss him in the locker room as a leader."
Wade, who started opposite Allen the past two weeks, touched on the same theme following Saturday's game. Seeing Allen carted off the field on a rolling stretcher was painful.
"Jason's like a big brother to the entire secondary," Wade said. " It hurt me a lot to see him go down. I look at him as an inspiration each and every down. To see him go down like that and not be able to carry himself off really hurt. "
Allen led Tennessee and the Southeastern Conference in tackles as a junior safety in 2004. He spurned the NFL Draft to return for the 2005 season under the stipulation he'd be used as a cornerback. Through four games he was again leading UT in tackles (33). He also had two pass breakups, a forced fumble and a sack.
Fulmer recently compared him to ex-Vol Gibril Wilson, a strong safety known for his thunderous hits.
"People probably underappreciated Gibril Wilson here," the coach said. "Jason's the same kind of guy with better pass coverage skills."
As for Allen's return to corner, Fulmer said he did "a fantastic job of keeping himself in the mix with the run" and also did "a really nice job of being where he's supposed to be and covering well. I couldn't ask for it to have gone any better."