Mitchell registered just two tackles in the opener against Alabama-Birmingham, while Mayo came off the bench to record four tackles and two assists.
Defensive coordinator John Chavis isn't given to lavish praise but he has great things to say about Mayo.
"If you're a backup here, you're only one play away from being a starter, and we felt really good about where he was as a backup," Chavis said. "Now he's got an opportunity to start.
"I feel real good about him. He's made great progress. He had a really good spring and played well in the first ballgame. Now it's time to go play a big ballgame with him."
Like Mitchell, Mayo has good size and great speed. Mayo also has a knack for being in the middle of the action.
"He's got a good nose for the football," Chavis said. "He's a full-speed player. He tackles well. He's a really, really good athlete, and that's what you're looking for."
Mayo's athleticism could be especially crucial this weekend against Florida. The Gators' spread option offense puts tremendous pressure on opposing linebackers – both in run support and pass coverage.