College football Week 15 SP+ rankings

Florida's loss to LSU on Saturday night shook up the national title race a good amount, offering an increase in Playoff odds to both Ohio State and Texas A&M, among others. But it didn't do much to change the top SP+ ratings, where Alabama, Clemson and Ohio State -- only one of whom actually played on Saturday -- remained the top three.

North Carolina predictably jumped into the top 10 following a blowout of Miami, while the Hurricanes, like Wisconsin, fell a good amount. But as we approach Championship Weekend, last week's title-game projections are more or less this week's: Alabama will head to Atlanta as a projected 10-point favorite over the Gators, Ohio State will have about a 17-point advantage over Northwestern, and Clemson, this time with Trevor Lawrence, holds about a 5.5-point advantage in a rematch with Notre Dame.

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.

More than ever, it's 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.