With three weeks to go in college football's 2021 regular season, the College Football Playoff chase remains a bit uncertain (outside of Georgia's nearly guaranteed spot, anyway). But from a power ratings perspective, the hierarchy remains unchanged. In this week's SP+ ratings, Georgia still holds a solid lead in the top spot, followed by Ohio State, Alabama and, after a pretty significant gap, everyone else. No. 3 Bama is 4.5 points ahead of the No. 4 team -- the same distance that separates No. 6 from No. 15.
What is SP+? In a single sentence, it's a tempo- and opponent-adjusted measure of college football efficiency. I created the system at Football Outsiders in 2008, and as my experience with both college football and its stats has grown, I have made quite a few tweaks to the system.
It is, as always, important to note that SP+ is intended to be predictive and forward-facing. It is not a résumé ranking that gives credit for big wins or particularly brave scheduling -- no good predictive system is. It is simply a measure of the most sustainable and predictable aspects of football. If you're lucky or unimpressive in a win, your rating will probably fall. If you're strong and unlucky in a loss, it will probably rise. It is a look at how teams should likely perform moving forward.