Seeing a team crush its playoff opponents can inspire confidence in its fans going into the Super Bowl. A team patched up its weaknesses against strong opponents, and is playing with confidence and chemistry. And if nothing else, being able to blow out payoff teams seems to suggest that your team is really, really good. So does playoff dominance en route to the Super Bowl suggest that a team is more likely to win it all than a team that narrowly squeaked its way into the game?
Not. At. All.
Blowing out other teams on the way to the Super Bowl is surely the lower-stress and more enjoyable way to make your way into the biggest American sporting event, but doing so doesn’t suggest that you’re more likely to win it all than a team that barely got in. We can see this in a couple of ways. The first, more “traditional” way of measuring a team’s dominance in wins is to look at its point differential — how many points a team score minus how many its opponents scored — per game. We see that there is really no correlation between a team’s point differential in its playoff games and whether it wins the Super Bowl. In fact, the numbers suggest that the impact of a team’s point differential on its Super Bowl result is well below one percent, and when we plot the Super Bowl matchups by loser’s previous playoff point differential versus winner’s previous playoff point differential, we can see that the winning Super Bowl team was just as likely to have underperformed the team they beat in their previous playoff games as to have outperformed them. If performing better in the playoffs more than your Super Bowl opponent suggested that you were more likely to win, we would expect that most of the data points would be above the red line. However, that’s not the case.
The second way we can measure a team’s dominance is, instead of looking at the point gap between a team and its opponents, looking at the ratio of the points a team scores to the points it allows. So, for instance, a team that wins a game 28 to 14 would have a ratio of 2. This captures the idea that we usually don’t think that a team that wins a game 49 to 35 as having dominated the game whereas we often think that a team that wins a game 17 to 3 smashed their opponent, even though the point differential is the same in each game. Looking at Super Bowl matchups this way, we get the same lesson as before.
I was surprised to learn that how easily a Super Bowl team’s path to the game was has had nothing to do with whether that team won the Super Bowl. I would have thought that teams that dominated their playoff opponents would be more likely to win it all than teams that barely got by (and I’m confident a similar analysis in, say, the NBA, would show very different results…) Winning by a lot against quality opponents usually indicates that a team is better than another team that barely beats similarly strong opponents, and, because of the way NFL playoffs work, the greatest teams should have slightly worse opponents on average in at least one of their games than the less strong teams. That there is no correlation between how easily a team makes its way to the Super Bowl and how likely it is to win the game is a testimony to the NFL’s parity and the greatness of the Super Bowl as America’s top unofficial holiday.