Brent Venables
Scott Frost
Tee Martin
Maybe Chip Kelly. Not totally sold on him succeeding in Knoxville, but maybe.
Most of the other names people are saying are unrealistic pipe dreams. Gruden has been out of coaching for almost 10 years. He's never coming back.
Jim Bob Cooter is a great offensive mind, but has virtually no experience in the college game, no head coaching experience, no recruiting experience, etc. Could have high upside, but he's extremely high risk given all that.
Petrino would take the job in a heartbeat, but I don't want him.