I've written about strength of schedule on many occasions over the years. Way back in 2010, I introduced the concept of measuring schedule strength from the top down, calculating the likelihood of an elite team running the table as a more effective way to measure the merits of national championship contenders. I kicked off my 2014 season preview in advance of the first iteration of the new College Football Playoff with the introduction of "degree of difficulty," designed to measure record (rather than possession efficiency) against schedule. Last season I adjusted my approach again, this time articulating the distinctions between the challenge of facing a given schedule as an elite team, as a merely good team, and as an average team.
My mathematical approaches to presenting schedule strength have evolved, but my fundamental approach to the problem of schedule strength has remained consistent: measuring it requires context and perspective. College football team schedules vary significantly, even within conferences, and one schedule strength metric does not fit all. Some schedules are top-heavy, some are bottom-heavy, and some are well-distributed, and the strength of team that faces the given schedule has to be factored into the equation along with the strength of the opponents themselves. The challenge a playoff contender faces en route to an undefeated or one-loss season must be measured on different terms than the challenge a mid-tier team faces en route to piecing together enough wins for bowl eligibility. And I believe it's important to share schedule strength data not simply as a way to rank and compare teams, but also to express the meaning of the metric itself.
Heading into conference championship weekend, we're staring down yet another College Football Playoff debate punctuated by parsing the merits of who-played-who. Will LSU or Ohio State have the most worthy resume of a No. 1 overall seed if they win their respective conference title games this Saturday? Will Utah or Oklahoma have the most worthy resume of a spot in the playoff field if they also win this weekend? Those debates shouldn't be settled exclusively by schedule-strength arguments, but the selection committee needs to have an informed perspective on schedule strength to have an argument at all.
I'm presenting 2019 strength of schedule data this week in nine different ways. I'll explain each, accompanied with a table snapshot highlighting the leader in the given measure. The first three schedule-strength metrics have been part of the FEI, OFEI, and DFEI ratings tables throughout the year.
OA represents each team's per-possession opponent adjustment, the difference between its raw overall possession efficiency and its opponent-adjusted overall efficiency in my FEI ratings. Auburn has faced the toughest set of opponents on a per-possession basis over the course of the year according to this schedule strength measure. On average, I'm making an adjustment of 0.39 points per possession for Auburn. In other words, a possession that netted a touchdown on the scoreboard was worth 7.39 points for the Tigers, on average, in their FEI rating due to the strength of their opponents.
OOA represents each team's per-possession offensive opponent adjustment, measuring the strength of the defenses that team faced, the difference between its raw offensive possession efficiency and its opponent-adjusted offensive efficiency in my OFEI ratings. South Carolina leads the way here, with an adjustment of 0.41 points per offensive possession.
DOA represents each team's per-possession defensive opponent adjustment, measuring the strength of the offenses that team faced, the difference between its raw defensive possession efficiency and its opponent-adjusted defensive efficiency in my DFEI ratings. Auburn heads up this list as well, with an adjustment of 0.51 points per defensive possession.
The next two schedule strength metrics are from the perspective of an elite team, defined as a team two standard deviations better than average, or approximately 1.0 points per possession better than an average team. In the FEI ratings, such a team would rank seventh this week (just behind Utah and ahead of Georgia). Such a team would have finished the year ranked fourth in 2018, behind Alabama, Clemson, and Georgia.
EL represents the average number of losses an elite team would have against the team's schedule, calculated in a similar manner as FEI game projections and taking into account the location (home/away/neutral) of the games. Texas A&M has faced the toughest schedule according to this metric -- an elite team would be expected to lose 3.22 times on average against the Aggies' schedule. E1 represents the likelihood an elite team would have one or fewer losses against the schedule. Against A&M's schedule of FBS opponents, an elite team would have only a 7.3% chance of going 10-1 or better.
Texas A&M faced Clemson (current FEI No. 2), Alabama (No. 3), LSU (No. 4), Georgia (No. 7), and Auburn (No. 12) this year, and only had two of those opponents at home in College Station. That's a murderous schedule for an elite team to navigate, but the challenge after those five teams was not very significant. Texas A&M didn't face another opponent ranked in the top 40. As a result, the Aggies don't have the nation's toughest schedule through the lens of a less-than-elite team.
I'll pause here to note that though my numbers do not consider FCS games, they are effectively counted as "100% win likelihood" games in the strength of schedule calculations. A schedule that includes one or more FCS opponents isn't discounted per se, but one that includes a full complement of 12 FBS opponents has no such "100% win likelihood" opponents. Each FBS opponent faced, even a weak one, makes for an incrementally tougher schedule with this approach.
The next two schedule strength metrics are from the perspective of a good team, defined as a team one standard deviation better than average, or approximately 0.5 points per possession better than an average team. In the FEI ratings, such a team would rank 24th this week (just behind Louisiana Lafayette and ahead of Navy). Such a team would have finished the year ranked 22nd in 2018. GL represents the average number of losses a good team would have against the team's schedule, and G3 represents the likelihood that team would lose three or fewer games.
The last two metrics are from the perspective of an average team. AL represents the average number of losses an average team would have against the team's schedule, and A6 represents the likelihood that team would lose six or fewer games. In each of these measures, South Carolina's schedule ranks as the nation's toughest.
How do the playoff contenders measure up? Schedule strength ratings for all 130 FBS teams through these nine lenses can be found here, and the table below extracts the schedule ratings for the top seven teams in this week's College Football Playoff ratings.
There's not much surprise in the order in which these ratings stack up. LSU and Ohio State have faced the toughest challenges of the group to date, winning two more games than an elite team would on average against their respective schedules. Clemson has faced the weakest of the group thus far, and won't have a particularly tough ACC Championship Game opponent either. Of the remaining challengers, Georgia has the edge and is the only one that controls its own destiny -- an SEC Championship Game victory over LSU will ensure a playoff appearance for the Bulldogs, while the others are hoping to take their spot if Georgia falls against LSU.
Oklahoma, Utah, and Baylor will each get a boost in the EL and E1 ratings columns after conference championship games are played, but none more dramatically than the others. An argument can certainly be made that all else being considered, Oklahoma's edge over Utah in schedule strength could slide the Sooners ahead of the Utes after this weekend. On the other hand, Oklahoma already has a schedule strength argument over Utah and they're behind the Utes this week -- Utah's more dominant victories appear to be swaying the committee more than schedule strength.
So how much will strength of schedule matter in the end? And how much should it? Oklahoma's schedule is ranked about 33 spots tougher than Utah's through Week 14, and that translates to an extra 0.44 expected losses for an elite team and 19% stronger chance of having at least one loss on the season. Is that dramatic enough of a difference? We may find out the answer to this question this weekend, assuming the higher ranked teams all win. The selection committee may not articulate its strength of schedule measure, but we can be as precise as we need to be.
2019 FEI Ratings (through Week 14)
The Fremeau Efficiency Index (FEI) is a college football rating system based on opponent-adjusted possession efficiency, representing the per possession scoring advantage a team would be expected to have on a neutral field against an average opponent. Unadjusted possession efficiency (PE) is calculated as a function of offensive, defensive, and special teams game splits. Schedule strength is represented by each team's average per possession opponent adjustment (OA). Opponent-adjusted offense ratings (OFEI), opponent-adjusted defense ratings (DFEI), and opponent-adjusted special teams ratings (SFEI) are calculated in a similar manner as overall FEI ratings. Team records against all FBS opponents (W-L) and against opponents ranked in the FEI top 10 (v10), top 20 (v20), top 30 (v30), top 40 (v40), and top 50 (v50) are also provided.
Ratings and supporting data are calculated from the results of non-garbage possessions in FBS vs. FBS games.