We’re back (again)! That pesky thing called life got in the way for a bit, but thankfully I was able to carve out a little time today and get the probability matrices going again. TL,DR: It still effectively looks like a one-game season, but some opponents have the potential to be annoying. Also, the uncertainty in this season means we’ll likely see some wackiness every week, like, I don’t know, Alabama and Ole Miss combining for 111 points and 1,370 yards. Whee!
Recapping the methodology for these articles: These aren’t actual SP+ win probabilities, as SP+ creator Bill Connelly doesn’t publish those regularly. He does though publish his SP+ ratings every week for all FBS teams. We used a slightly tweaked version of the formula that Reddit poster rcfbuser (account deleted, pour one out) reverse-engineered using these ratings to get close to SP+’s published probabilities. That formula does some probability magic on the differential in SP+ rating for the two teams (with a bump for home field, and yes, the bump is smaller this year given the smaller crowds), and voilà . The FPI win probabilities are updated weekly by ESPN, so those are the real deal.
SP+ can be a bit wonky from week to week at first, as creator Bill Connelly intentionally works in a lot of volatility early in the season to account for reality vs. projections. Keep that in mind when you see wild swings from one week to the next; those are by design, not by accident. SP+ measures offensive and defensive explosiveness and efficiency on a per-play basis. FPI is ESPN’s proprietary metric and is much more of a black box, but we do know that it rests heavily on expected points added, which is a pretty solid advanced stat and also a per-play number.
Post-Week 5 Update – SP+ Matrix
As you move down each column, you find the probability of Notre Dame owning that many wins at that point of the schedule. In the first couple of rows, you can see that the probability of owning 0 wins through week 2 is 0% and two wins is 100%, since we already won. In the last row, we’re tracking how much the probability of each win total has changed from the previous week. This is a function of our own outcomes, the quality of play that led to those outcomes, and SP+’s changing perceptions of our past and future opponents.
The 7.7% figure at the end of the Wake Forest row reflects our probability of winning out per SP+. That may seem low – and it did drop 1.2 points from the week before – but it’s actually a pretty solid number for this point in the season. For reference, after three weeks in 2018 the SP+ win-out probability was around 3%.
Post-Week 5 Update – FPI
As in our last update, FPI is similar to SP+ for our softer opponents, more bullish on our two non-bad opponents (Pitt and UNC), and much more bearish on Notre Dame against Clemson. I can’t make any kind of solid conjecture as to why this early in the season, but that’s something that bears watching.
Week by Week Game Trends
| SP+ | FPI | |
|---|---|---|
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Here we’ll track how the probabilities move from week to week. I’m not surprised to see SP+ shift down given our at-times uneven performance on Saturday, but I am surprised that it shifted down so significantly for most of the teams. Something to keep in mind is that SP+ moves from week to week not only based on team performance, but also on pre-season projections receiving less weight with each passing week. And, as we’ve noted in the past, Connelly has designed it to swing quite a bit early in the season so it adjusts better to reality.
Anyway, the disparity between the two metrics will be interesting to track.
Closing Thoughts
Louisville will pose a good challenge for the Irish defense; they have a quarterback with plus mobility in Malik Cunningham and, in RB Javian Hawkins and All-American WR Tutu Atwell, two of the most dynamic athletes Notre Dame will face all season. On the flipside, their defense is terrible – currently 96th in SP+, which makes me wonder if the BVG hangover can stretch to two seasons. What I’m saying is, it probably won’t be a full-team test. After that, though, the Irish will face the 12th (Pitt), 35th (Georgia Tech), and 4th (Clemson) ranked defenses. The offense needs to take advantage of the opportunity to fine-tune this weekend, because the three weeks after that will require it to be a well-oiled machine.
At a higher level, the takeaway this week I think is that regardless of which numbers shifted where, Notre Dame remains a heavy favorite in at least six of its eight remaining games. The Irish are 5th in the AP Poll, 7th in the SP+ rankings, and 8th in the FPI rankings. This is a good team. Let’s hope they play up to that ability.
One weird thought is that these same charts for Clemson probably have them with at least a 60% chance of winning each game (except against ND, which is 58% for them), with probably most games above 80%. I wonder if that makes the season a little boring for them?
Based on the limited interactions I’ve had with Clemson fans, not at all. To a certain extent I get it — they spent decades as a punchline in college football, so they don’t really mind beating almost every opponent by 40 and playing one or two big games a year.
There is definitely evidence Bama fans have gotten bored with their pathetic scheduling, however.