Just as a reminder, when Nick Saban was Dan Mullen's current age, he was at 12-11-1 at Michigan State. Saban didn't win his first national title till age 52, after taking the job at LSU, where he had more resources and a much better recruiting footprint than at Michigan State.
This idea that Dan Mullen would be a mediocre hire is rubbish. He's by far the most successful coach in modern Mississippi State history. So many people here at VN are dramatically underestimating how much of a disadvantage Dan Mullen is competing with at Miss State versus teams like Alabama, LSU, Texas A&M, and Auburn. He's 23 - 23 over the past 6 seasons in the SEC West competing against teams with vastly better resources. That's a better conference record than James Franklin had against much tougher competition in the SEC West.
He turned Alex Smith into a top NFL prospect, Tim Tebow into a national championship QB at Florida, made Dak Prescott elite, and this season he's 7-3 with a 2-star QB in Nick Fitzgerald. The dude knows how to coach up QBs! Imagine what he could do with former 5-star and #1 ranked Dual Threat QB Jarrett Guarantano!
With Tennessee's resources, Mullen could achieve more than he has at Miss State.