Michigan is showing signs of wear and tear, but with a 2.5-point home-field adjustment, the Wolverines are still a six-point projected home favorite over Ohio State, according to the updated SP+ rankings.
Michigan has ranked first in SP+ since Week 5 and held steady after Week 12's results, but to the extent that trends matter, an interesting one has emerged: The Wolverines have underachieved against SP+ projections by 6.3 points per game over the past three weeks, while the Buckeyes have overachieved by 4.0 PPG in that same span and haven't actually underachieved against projections since Week 2. Ohio State remains third overall, and the top three -- Michigan, Georgia and the Buckeyes, with Oregon lingering nearby (so maybe top 3.5?) -- have formed a clear top tier.
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: