Some key milestones for comparing Josh Heupel with the four best coaches in Vols history:
To surpass John Barnhill, the Vols' 4th best coach: win an SEC championship. Barnhill has an incredible win percentage, even better than the General (32-5-2 over four seasons, .846 win rate), but he never won a title.
To surpass Johnny Majors, our 3rd-best coach (some folks flip Majors and Barnhill): win a national championship. Johnny did win one national crown, but that was for Pitt. So it doesn't count as a Volunteers accomplishment. Josh leapfrogs Johnny if he does that, particularly since Johnny's win rate (.645) wasn't nearly as good as the other top coaches.
To overtake Philip Fulmer, our 2nd-best coach: win two national titles, or one national title with three+ SEC crowns. It will help a lot if Josh's win rate is .750 or better, since Fulmer's was a very respectable .745.
To catch The General: this is a tall order. Recency bias will make Josh the most beloved well before he actually out-performs Neyland, but objectively speaking it would take 4+ national titles, 8+ conference crowns, and a win rate well north of .800 (Neyland went .829).
That's when we'll know.
Go Vols!