SP+ had a pretty good lay of the land in Week 5, going 56% against the spread and missing games by an average of only 12.1 points per game. Those are strong numbers, but we still saw plenty of unexpected results: Georgia struggled far more against Missouri than projected (same with Penn State vs. Northwestern), Oklahoma laid an egg against TCU, Minnesota fell to Purdue after posting four weeks of absolute dominance, and Utah destroyed Oregon State, among other games.
The result? No changes among the top four teams but plenty of surprises thereafter. We headed into this season not really knowing who the fourth-best team was after a strong top three, and while Michigan has given SP+ an answer in that regard, the No. 5 spot remains completely up for grabs.
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. 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.