College football Week 6 SP+ rankings

We've got only two more Saturdays until the Big Ten begins its late-fall football campaign, and only two more after than until the entire Power Five is involved and active. With so many top teams having yet to kick off -- eight of the current SP+ top 16, in fact -- it's hard to see much movement atop the rankings just yet.

Clemson and Alabama are doing a little dance for the No. 2 spot, however.

Bama started second, fell to third after falling asleep in the second half against Missouri and jumped back to second after a dominant win over A&M. But while Bama was giving up record points and yards in a shootout win over Ole Miss, Clemson looked phenomenal in a 42-17 win over Miami. That was enough to push the Tigers back to second.

(Ohio State, meanwhile, remains first. Sorry, unbeaten Ohio State remains first. That sounds better.)

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.

SP+ is intended to be predictive and forward-facing. That is important to remember. 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.