Backup quarterback Zach Metterberger is being prepared to start in case Mariota can't play.
Tennessee coach Ken Whisenhunt was non-committal on whether or not he would start Mariota, and said he doesn't have a firm rule about whether a player who didn't practice all week can start a game.
"If it was a couple months ago, I'd really have some concerns about it, but after having played as many reps as he has and gone through the plan, you're a little bit less strict about that," Whisenhunt told reporters. "But it's still important. I think tomorrow will be a big day as far as determining that."
Mariota, the No. 2 overall pick in the 2015 NFL draft, has passed for 1,239 yards, nine touchdowns and five interceptions through five games.