College football SP+ rankings after Week 4: SEC games, Pac-12 return shake things up

Nix does it all with his arm ... and his leg (1:43)

Bo Nix impresses with two punts inside the 10-yard line, then he shows off his arm, throwing three touchdowns in Auburn's win over Kentucky. (1:43)

The combination of a couple of jarring upsets and the SEC's presence at the party made Week 4 of the college football season feel like the first true college football weekend of the year. And there was a decent amount of fallout from it in the latest SP+ rankings.

Below is this week's piping hot batch of SP+. As with last week, I'm now including the latest FBS teams that have committed to playing this fall -- the Pac-12, MAC and MWC all announced plans to jump in the pool this past week -- even though none of them will play for a few more weeks. That means we continue our streak of a new denominator each week: all 130 FBS teams were included in the preseason rankings, then 77 after Week 2, 91 after Week 3 and now 126 after Week 4. Nothing about this season is normal, but in theory we might stay at 126 for a while.

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. That is important to remember. 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 numbers.

This week's movers

Moving up

Looking at where teams would have been ranked last week had Pac-12, MWC and MAC teams been included (so we can compare apples to apples), and comparing them to this week's rankings, seven teams moved up at least 10 spots:

  • Kansas State: up 21 spots from 75th to 54th

  • Virginia Tech: up 17 spots from 34th to 17th

  • Texas State: up 14 spots from 118th to 104th

  • Mississippi State: up 13 spots from 51st to 38th

  • Georgia Southern: up 12 spots from 108th to 96th

  • Virginia: up 10 spots from 43rd to 33rd

  • Tulane: up 10 spots from 71st to 61st

Sometimes we end up with fluky upsets in college football -- the ball is pointy, the players are young and unlikely things happen. Neither KSU's nor MSU's upsets had much of a fluke factor, though.

Using my post-game win probability metric -- in which I take all the key, predictive stats from a given game, toss them into the air, and say "With these stats, you could have expected to win this game X% of the time -- Kansas State's 38-35 win over Oklahoma came with a 40% likelihood, while Mississippi State's 44-34 upset of defending national champion LSU was at a whopping 95%. The scores mostly reflected the stats, and in the case of LSU, the 10-point loss was kind to the Tigers. KSU and MSU therefore rose accordingly in the ratings.

Virginia Tech moved up even further than MSU, however, thanks to a truly dominant performance against NC State. SP+ projected the Hokies to win by nearly two touchdowns, and not only did they win by 21, it could have been far worse. They averaged 9.6 yards per play to the Wolfpack's 4.2 in the first half and let their foot off the gas a bit in the second.

Biggest fall

Seven teams fell by at least eight spots compared to where they would have been ranked last week.

  • Troy: down 20 spots from 60th to 80th

  • Kentucky: down 19 spots from 24th to 43rd

  • LSU:down 13 spots from 12th to 25th

  • Pitt: down 11 spots from 25th to 36th

  • Army: down nine spots from 63rd to 72nd

  • Florida State: down nine spots from 48th to 57th

  • South Alabama: down eight spots from 109th to 117th

Kentucky's 29-13 loss to Auburn played out as a tossup -- Kentucky committed a couple of devastating turnovers that allowed Auburn to take the lead before the Tigers tacked onto it later on. SP+ didn't necessarily see a tossup, though. Auburn's success rate was 10 percentage points higher than UK's (47% to 37%), and the Tigers executed a million times better in the red zone. AU's post-game win expectancy ended up at 98%.

The most surprising name on this list might be Pitt. The Panthers moved to 3-0 with a 23-20 win over Louisville, but their post-game win expectancy was only 32%; their defense was excellent as always, but the offense was inefficient, particularly in the red zone. They needed a little turnovers luck to get over the finish line, and they fell a bit in the rankings. (Dropping 11 spots for that seems harsh, but note how closely bunched the teams in that range are -- they're only 1.9 adjusted points per game outside the top 30.)

As the SEC turns

The SEC offered up quite a few surprising results in its return to action. SP+ is not designed to react much to a team's first game of the season, but there was still a decent amount of movement, up and down. You see the LSU and MSU movement above, but here's how other teams fared.

  • Alabama moved down one spot, from second to third, after an easy win over Missouri. That probably won't make Tide fans happy, but the top three are still comfortably ahead of the field. Missouri, meanwhile, moved from 47th to 48th.

  • Despite a dreadful start to the game, Georgia eventually performed about as expected against Arkansas. The Dawgs' offense justifiably fell from 37th to 50th, but with lots of other defenses struggling, their top-ranked D allowed them to remain fourth overall. Arkansas also remained about the same, slipping from 73rd to 75th.

  • If Kentucky moved down a decent amount, you'd probably expect a similar rise from Auburn. You'd be correct! The Tigers hopped from 11th to fifth after a comfortable win over what had been projected as a top-25 team.

  • Florida never let Ole Miss stay too close in Saturday's 51-35 win, but the Gators slipped from fifth to eighth because their defense slipped from third to 17th after allowing 613 yards and 7.9 yards per play. We might find that the Ole Miss offense is elite or close to it, however, and if that turns out to be the case, SP+ will adjust Florida's defensive ratings accordingly. (Ole Miss also slipped a bit, from 37th to 44th. SP+ doesn't like points, apparently.)

  • Texas A&M outgained Vanderbilt by three yards per play and held a 42%-31% success rate advantage; the Aggies only won, 17-12, but SP+ saw a game that was a comfortable win more often than not. It only dropped A&M from 14th to 19th, while Vandy rose slightly, from 114th to 110th.

  • Tennessee produced a 76% post-game win probability against South Carolina and typically would have won by more than the 31-27 margin suggested. The Vols still slipped a bit (from 21st to 24th), but only a bit. The Gamecocks, meanwhile, inched from 35th to 34th.