It’s nothing new that SEC programs are projected to have the top defenses in college football year-in and year-out. It just begs the question: which teams will be at the top?

According to ESPN’s Football Power Index, Alabama, LSU and Florida will have the top three defensive units in the country. Texas A&M is the only other team to be ranked in the top 10 at No. 7.

Here’s how the site explains how it ranks the defenses:

The first and most important is prior years’ performance on offense, defense and special teams, with the most recent year counting most. Opponent-adjusted expected points added (EPA), the backbone of all of ESPN’s college football metrics, is utilized to measure performance in prior seasons. The second-most important factor is returning starters, which is provided by ESPN Insider Phil Steele. The final two pieces of preseason FPI hold significantly less weight but are important when predicting team strength. FPI utilizes a four-year average recruiting ranking of four systems (ESPN, Scouts, Rivals and Phil Steele) to measure talent on a roster.

What’s interesting is that the No. 1 and No. 2 projected units — Alabama and LSU — both have new defensive coordinators. Jeremy Pruitt takes over for Kirby Smart at Alabama, while Dave Aranda takes over for Kevin Steele at LSU.

I don’t think anyone will argue with Alabama having the top projected defense. Although the unit loses defensive linemen A’Shawn Robinson and Jarran Reed, along with star linebacker Reggie Ragland and defensive coordinator Kirby Smart, there’s reason to believe the Crimson Tide’s unit could be as good or better this season. The defensive line isn’t taking a step back, and it’s easy to see the Tide are two- and three-deep at virtually every position.

As LSU transitions under Aranda, it is the most interesting program to watch. LSU and Les Miles pulled a stunner getting Aranda from Wisconsin, and just how that program — and unit — gels under Aranda will be fun to watch.

Obviously, Florida loses some talent in CB Vernon Hargreaves, LB Antonio Morrison and DL Jonathan Bullard, but there’s talent, nonetheless. Florida’s linebacking corps is one to keep an eye on, because it’s somewhat thin. The secondary and defensive line should be very good.