College football's post-Week 13 SP+ rankings - ESPN

We know one thing: Ohio State has earned the right to be called the best team in the country (on paper). Beyond that, Week 13 of the college football season only blurred the picture. The No. 2 (Alabama) and No. 4 (Ole Miss) teams in last week's SP+ rankings both lost, No. 3 Texas looked lost offensively, and No. 7 Penn State thought hard about losing, too.

Ohio State expanded its lead in this week's SP+ ratings to a comfortable degree, but we've now got a three-loss team at No. 2, and the second- and ninth-best teams are separated by only 3.5 points, barely more than the typical home-field advantage adjustment (2.5).

It's getting messy out there! I love it! Below are this week's SP+ rankings!

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-looking. 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.

Let's take a look at the teams that saw the biggest change in their overall ratings. (Note: We're looking at ratings, not rankings.)

Here are the 10 teams that saw their ratings rise the most this week:

Akron: up 3.8 adjusted points per game (ranking rose from 132nd to 125th)

Bowling Green: up 3.7 points (from 75th to 63rd)

UNLV: up 3.5 points (from 46th to