College football's post-Week 4 SP+ rankings

Remember when we entered the 2023 college football season thinking we had a "top four and everyone else" situation? That is no longer the case. Four weeks into the season, we officially have a battle royale for the top spot.

In the final SP+ preseason projections, the top four teams (Georgia, Ohio State, Michigan and Alabama) were pretty well separated from the pack. Only 1.2 points separated No. 1 from No. 4, but 5.3 separated No. 4 from No. 5. Now? We have only 5.9 points separating No. 1 from No. 10. Michigan is your new No. 1 -- it's the fourth time the No. 1 ranking has changed hands in four weeks -- but with the weight of opponent and conference adjustments kicking in far more after four games, the Pac-12 as a whole has made a pretty serious move up the charts. The top three of Michigan, Georgia and Ohio State remains familiar, but three Pac-12 teams and two Big 12 teams are within reach of the No. 1 spot. This season could get very, very interesting in the coming weeks.

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 indeed 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.

Here are the full rankings: