The only two stats the ultimately matter in determining how successful a defense is are (in this order):
1. PPP (aka PPD) - points per possession (aka points per drive): This tells the story much better than a simple "Total defense" number because it accounts for the different paces that different teams play at. We will probably have a significantly higher number of possessions to defend than we did in the CPJ years, so our total defense could look worse while our points per possession could be better. I like this better than sacks/TFL's/turnovers/etc because there are lots of different ways to be successful on defense (maybe a lot of sacks or turnovers or maybe a lot of 3 and outs). So, what I really want to know is where we stack up on this with the rest of the country. What is the PPP (or PPD) ranking?
2. YPP - yards per play: This also says a lot about how successful a defense is. The PPD stat could be affected by the starting field position (which is a product of special teams and offense more than the defense) and by turnovers or lackthereof (a lot of times turnovers have more to do with luck than with defensive play, which can change from year to year, ypp takes this out of the picture). What is the YPP ranking?
These are ultimately the only stats that matter for determining the level of success for any defense.
For now, since we can't really know anything about our D yet, I'd be interested in those rankings for MSU, UF, and Temple immediately before, during, and after CGC's time as DC/HC at those programs.