The actual value of Playoff seeding (and why 2019 might have the best field ever)

The Playoff committee’s rankings are designed to give the #1 seed a couple rewards in the tournament. That team gets to play the least-impressive top-four team, in the committee’s mind, and gets to play in the semifinal bowl that provides less of a travel disadvantage.

The last part doesn’t matter a whole lot, because these games will rarely be all that close to campuses. The former hasn’t always meant much, either. Two #4 seeds beat #1 teams in the CFP’s first five years, and no #1 won the whole thing in that span.

2019’s bracket sets up differently, providing ample reason to believe the #1 spot provides more value than ever before. While Ohio State and LSU were both almost certainly in, even if they’d lost during championship weekend, they had extra motivation to fight for the top spot. LSU did just that by crushing Georgia, while Ohio State struggled somewhat with Wisconsin.

There are two factors:

1. 2019’s #4 seed appears to be slightly weaker than all-time #4 seeds by average, and
2. 2019’s #3 seed rates much stronger than normal.

With those two factors combined, the gap between #3 and #4 made getting 2019’s #1 seed something truly worth playing for.

The typical gap between #1 and #4 hasn’t always been very big.

In the first five years of the CFP, the #1 seed was favored over the #4 seed by anywhere between 3.5 and 15 points, an average of about six.

One day after 2019’s Selection Sunday, #1 seed LSU was a 13-point favorite over #4 Oklahoma. That’s even greater than I anticipated in my December 4 edition of The Read Option newsletter.

Let’s show our work.

For the purposes of this analysis, let’s assume that Ohio State, LSU, and Clemson all win. This is an assumption that is more likely than not, according to the Vegas odds (about 60%). This means Georgia would be out of the running, leaving Utah and Oklahoma as the primary options for the #4 spot.

If all three win, Clemson would not jump up, meaning they would be locked in to the #3. The race for #1 would come down to Ohio State or LSU.

The first question becomes, then, how big is the gap between Ohio State/LSU and Utah/Oklahoma?

To answer this I used an average of SP+ and FPI. This is an imperfect, but close, way to approximate Vegas spreads in most cases, assuming no major injuries to QBs need be accounted for.

That rough method suggests a Vegas spread of Ohio State by 12 over Utah and 11 over Oklahoma. It would put LSU as 7.5 points better than Utah and 6.5 better than Oklahoma. Those are significant spreads for a game between alleged top-four teams, but they are not wildly out of line with what we have seen in the past between the #1 and #4 seed.

The average SP+ rating for a #4 in the CFP is 26.7. And 2019 Oklahoma is pretty on par with most of the #4 seeds, as 2017 Alabama really skewed the average.

1. 2017 Alabama: 33.5
2. 2016 Washington: 26.7
3. 2014 Ohio State: 25.8
4. 2019 Oklahoma: 25.8
5. 2018 Oklahoma: 24.9
6. 2015 Oklahoma: 22.7

The even bigger question: how much better is 2019 Clemson than the typical #3?

Following the Buckeyes’ comeback win against Wisconsin, Ohio State head coach Ryan Day stumped hard to be #1. There’s a reason.

The early spreads (#3 Clemson by two over #2 Ohio State, and #1 LSU by 13 over #4 Oklahoma) affirmed the #2 team that drew Clemson would likely face a much more difficult semifinal than the #1 team that got Oklahoma.

Clemson is, by the power ratings, the best #3 seed in Playoff history, about a full touchdown better than the average.

Through the CFP’s first five years, the average SP+ rating for a #3 seed was 22.78. At 29.3, Clemson rates higher than that average by a lot, though the average is dragged down by 2015 Michigan State, by far the worst-rated CFP entrant ever, and Clemson is the highest-rated #3 seed in the history of the CFP. 2019 also features by far the highest rated 1-2-3 trio yet.

1. 2019 Clemson: 29.3
2. 2014 Florida State: 28.5
3. 2017 Georgia: 26.7
4. 2016 Ohio State: 22.4
5. 2018 Notre Dame: 20.7
6. 2015 Michigan State: 15.6

The battle for the #1 seed was, if you believe the numbers, much more about avoiding Clemson than about getting Oklahoma.

Looking at the implied win probabilities of a team favored by 10 to 14 points, as opposed to a team with an even spread, we can see that the implied probability of winning goes from 50% (for a spread of 0) to just over 80%. In a championship setting, playing a game in which you are 80% likely to win, while the other two top contenders just have something like 50% against each other, is a huge advantage.

Overall, 2019’s Playoff field stands out as unusually highly rated.

The average SP+ rating for a #1 seed had been 30.54. LSU rates higher than that.

1. 2018 Alabama: 36.3
2. 2014 Alabama: 34.3
3. 2019 LSU: 31.8
4. 2016 Alabama: 31.7
5. 2017 Clemson: 26.4
6. 2015 Clemson: 24.0

And the average #2 through five years was 27.52. Ohio State grades about a touchdown better than that.

1. 2019 Ohio State: 35.4
2. 2018 Clemson: 29.7
3. 2015 Alabama: 29
4. 2016 Clemson: 28.7
5. 2017 Oklahoma: 25.5
6. 2014 Oregon: 24.7

So in addition to 2019 having a respectable #4 and the best #3 yet, the field’s combined rating of #1 and #2 seeds is likewise the best ever, slightly higher than the 2018 Alabama-Clemson duo.

Finally, here are all Playoff teams from 2014 through 2019, ranked by SP+:

1. 2018 Alabama: 36.3
2. 2019 Ohio State: 35.8
3. 2014 Alabama: 34.3
4. 2017 Alabama: 33.5
5. 2019 LSU: 31.8
6. 2016 Alabama: 31.7
7. 2018 Clemson: 29.7
8. 2019 Clemson: 29.3
9. 2015 Alabama: 29
10. 2016 Clemson: 28.7
11. 2014 Florida State: 28.5
12. 2017 Georgia: 26.7
13. 2016 Washington: 26.7
14. 2017 Clemson: 26.4
15. 2014 Ohio State: 25.8
16. 2019 Oklahoma: 25.8
17. 2017 Oklahoma: 25.5
18. 2018 Oklahoma: 24.9
19. 2014 Oregon: 24.7
20. 2015 Clemson: 24
21. 2015 Oklahoma: 22.7
22. 2016 Ohio State: 22.4
23. 2018 Notre Dame: 20.7
24. 2015 Michigan State: 15.6

That leads to a thought on a related topic:

An eight-team playoff would be fun. But with every expansion, the regular season loses a bit more drama. While there was no drama with the top teams in terms of making the Playoff, the high stakes of avoiding Clemson did provide some.

I’m not sure we’d get that with an eight-team field, because the difference between a #7 and #8 is not likely to be as great, due to the natural flattening of the bell curve of college football ratings.