College football SP+ rankings after Week 6

Week 6 of the 2021 college football season was the wildest and most thrilling yet for an increasingly wild and thrilling campaign. Alabama lost, Oklahoma and Texas played maybe the greatest game in the history of their storied rivalry, Ole Miss and Arkansas lived up to their "most underrated rivalry" status and then some, and the Big Ten got wild after sundown with Iowa outlasting Penn State and Michigan surviving a massive test from Nebraska.

On paper, however, it was a mostly orderly affair. The spread was pretty dialed in on average, and SP+ had its best week of the year from an absolute error perspective -- the absolute-value difference between projection and result. Order on paper and chaos on the field? Sounds pretty perfect! Let's see what the rankings have to say this week.

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 probably will fall. If you're strong and unlucky in a loss, it probably will rise.