I believe even as a DC he inherited good defenses everywhere he's gone. He gets a lot of credit for Florida and Miss State, but they already had good players and defenses when he came on. Someone can research it and correct me if I'm wrong (and I very well could be...I just have zero desire to research it), but it seem Collins just had to make sure he kept the train on the tracks when he took over as conductor.
I believe this to be true based on what I've heard for years. I was bored, so I decided to look into it.
All of the below figures below are based on DFEI (defensive efficiency), as it provides
a better representation of defense than "total yards." Figures taken
from this site.
I'm not going back to his time at Western Carolina 20+ years ago. We'll start at Florida International.
He was DC at Florida International in 2010. He took an arguably bad defense (DFEI ranked 103rd) and improved them 34 points to 69th in that one year. (For reference, Georgia Tech was ranked 76 in DFEI in 2023). Basically, took them from bad to the best in the Sun Belt. A respectable move, but against lesser-than-P5 competition...and without much margin of error (there were 4 other Sun Belt teams within 10 ranking points of FIU's ranking).
Florida International DFEI Rankings
2009 (year before, Phil Galiano) - 103rd
2010 - 69th
(Hired by Mississippi State in January 2011)
From there he went to be named Co-DC at Mississippi State, where he followed Manny Diaz (who had been hired away by Mack Brown in Texas). Began as Co-DC with Chris Wilson before assuming the head job. Kept it roughly the same ranking during his tenure with a couple of dips.
Mississippi State DFEI Rankings
2010 (year before, Manny Diaz) - 14th
2011 (Co-defensive coordinator) - 20th
2012 - 37th
2013 - 16th
2014 - 15th
(Hired by Florida in December 2015, before the Orange Bowl)
From Mississippi State, in 2015 he went to Florida, where he took over after Will Muschamp left and Jim McElwain came on. He took over the DC role from DJ Durkin, who had fielded fairly awesome defenses under Muschamp (who was also a defensive-minded coach, who got it done but simply didn't win enough games...
despite having a Top 5-ranked defense all but 1 year he was the HC.)
Florida DFEI Rankings
2014 (year before, DJ Durkin) - 3rd
2015 (1st year) - 15th
2016 - 8th
(Hired by Temple as HC on December 14, 2016)
So it could be argued that in 2016, he moved them up. This is still using only 1 year of his own recruits, so you could attribute it to him, or to DJ Durkin's recruits. Still, credit where credit is due (although we saw with Charlie Thomas and Keion White what a difference a few good players can make in a bad scheme).
He moved to Temple as HC in 2017, where the team's offense and defense slipped from where they were under Matt Rhule:
Temple DFEI Rankings
2016 (year before, Matt Rhule) - 38th
2017 - 38th
2018 - 48th
(Hired by Georgia Tech in December, 2018)
Of course, the job of a HC is a lot different than that of a position coach, so it's questionable how much we should grade him on this and his next stop. Including them for the sake of posterity, but take with a grain of salt.
As HC at Georgia Tech, his DFEIs were dreadful:
Georgia Tech DFEI Rankings
2018 (year before) - 103rd
2019 - 101st
2020 - 92nd
2021 - 112th
2022 - 41st (not really counting this, as things rapidly improved after he left).
So, all of that is to say - I think the characterization that he "rode the coattails" of some previously successful DCs is somewhat accurate, somewhat false.
If we're talking entire career, that's false. He did improve Florida International's defensive efficiency in the 1 year he was there, before leaving for Mississippi State.
However, if we're talking P5 jobs, I think it's pretty clear to say that he took over roles that some previously-successful DCs had been hired away from, and was able to in some cases maintain their level of efficiency, and in some cases worsen it (which usually seemed to get worse over time). None of them saw a big jump forward. Most simply languished, or stayed at close to the same level they were, before he bounced to a new job within a few years.
And if we assume that as HC he should at least be able to convey his defensive philosophy to his DC and team, I think we can say he wasn't able to do that.
------
TL;DR - It's pretty clear to me that he could be successful at UNC. But given that their DFEI last year was 77 (1 shy of Georgia Tech), it's going to be really interesting to see if he moves them up, or just keeps them close to where they've been under Gene Chizik. His P5 record suggests it will be more of the same.