This is the time of the year for joy and family and gifts--all that good stuff. But more importantly, it’s also the time for teams to jockey for playoff seeds. I get the sense that the conventional wisdom is that yes, seeds are somewhat important, but the notion that ‘just get in the playoffs and anything can happen’ is the dominant view. But as we'll see, seeding is critically important.
We’ve seen many wildcard teams make it to, and even win, the Super Bowl. There are four wildcard berths each year, and when we see a wildcard team make it to the Super Bowl, it’s noted, highlighted, and becomes part of the team narrative. No one remarks when the #3 seed makes it to the big game, despite it being less likely than either of a conference’s two wildcard seeds to make it.
Although it’s certainly true that ‘anything can happen’, that’s really only true from the perspective of a neutral observer. If you’re looking at the chance that any one of the four wildcard teams make it to the Super Bowl, you’ve got a pretty solid chance of seeing that happen. But if you look at it from the perspective of one particular wildcard team, your chances of going to the Super Bowl are relatively slim. It’s all a matter of perspective.
Football commentators certainly understand that seeds are important—a team would always prefer a higher seed. But I sense that they don’t fully appreciate how critical seeds are in the current NFL format. I hear talk about having home field advantage and having a week off to get healthy, but commentators seem to overlook the most important part of a playoff bye: It’s an automatic win in the first round. Maybe it’s overlooked because it’s so obvious, but those other considerations pale in comparison to the value of a free win. Right away, a bye practically doubles a team’s chance of making it to the Super Bowl. Doubles. A different way of thinking of the playoff format is that the top two seeds are the only two that actually ‘make the playoffs’, and the other four seeds must first win a play-in game.
To isolate just how critical seeding is, I calculated the chances each seed would make it to the Super Bowl due to seeding alone, ignoring differences in team strength.
I gave home teams a 60% chance of winning each game. Although the league-wide average is 57%, that number includes many mismatch games. When teams are close in ability, home field becomes more decisive. (Think of it this way: If the Packers played the Maryland Terrapins, the outcome wouldn’t depend at all on where the game was played.)
The probability for the #1 seed is straightforward. It’s just 0.6*0.6 because they need to win 2 home games. The #2 team needs to win 1 home game and has a 60% chance of being on the road in the conference championship (if the #1 seed wins its first game) and a 40% of being at home (if the #1 seed loses.) The total probability for the #2 seed would therefore be 0.6 * [(0.6*0.4)+(0.4*0.6)], which comes to 0.288. The probabilities for the other seeds become more complex but can be calculated the same way.
Here is how the probabilities work out for each seed. Also listed are the actual proportions of Super Bowl appearances since 2002 when the current format began. Keep in mind that the 'actual' numbers reflect the effect of both seeding and team strength, and that there are only 18 observations since '02, so they will be statistically noisy. Also note that the chances will not sum to 100% due to rounding. (Thanks go to my research intern for compiling the actual numbers.)
You can see that the #1 seed has about six times the chance of a wildcard team to make it to the Super Bowl. The #2 seed has nearly five times the chance. These are enormous differences, and they’re due to seeding effects alone.
Right now the 49ers and Saints are jockeying for the #2 seed in the NFC. The loser of that battle will fall from a 29% shot to an 11% shot at making the Super Bowl.
In the AFC, the biggest battle is between the Ravens and Steelers for what is most likely going to be the #2 seed, assuming the Patriots win out. The loser of the AFC North battle will sink to the #5 seed, cutting their chance of making the Super Bowl by over a factor of four, from 29% to 7%. In other words, the division champion quadruples its chance of making it to Indianapolis in February.
When it comes to making it to the Super Bowl, seeding alone is critically important, far more so than even team strength.