In Football Operations, one of our primary roles as a data and analytics team is to supply the league with metrics that help us better understand the game. One framework that we often use is win probability.
Models to estimate win probability have been around football for more than a decade, with several researchers (including Brian Burke, Trey Causey, and a trio of statisticians from Carnegie Mellon) having developed versions of their own. These models help assess each team’s chance of winning at any given point in a game.
Models use familiar inputs including score, down, distance, and field position, and also more subtle variables, including which team kicked off to start the game and the number of timeouts each team has left. During the 2019 offseason, win probability models were used by the National Football League’s Competition Committee to assess which penalty types have the biggest impact on game outcomes. In addition to penalties, we can use win probability formulas to derive metrics of game competitiveness and excitement.
The following chart highlight’s each team’s win probability curve through every game of the 2019 season (shown in gray), as well as an average win probability curve (shown for each team in its primary team color).
To find the teams that have played in the most exciting games, look for the grey curves with the biggest swings. Detroit, Indianapolis, Seattle and Tampa Bay have each averaged more than seven exciting plays per game — defined as those with at least a 10% swing in win probability — and their curves reflect that many games aren’t decided until the fourth quarter, when big swings in win probability tend to happen. Alternatively, most New England, Washington and Baltimore contests have been decided by the start of the fourth quarter and each of those teams averages fewer than four exciting plays per game.
We can also split into different time segments. On a per-quarter basis, no one has been better than Baltimore in the first quarter. The Ravens have typically started the second quarter with a 68% win probability, which implies that they earned an average of +18% in win probability per-game in the first quarter alone. Kansas City has dominated the second quarter (+17% per-game), Chicago has controlled the third quarter (+14%), and Green Bay has closed out games in the fourth quarter (+15%).
Which were the most exciting games of the 2019 season?
The Week 10 (link) Arizona and Tampa Bay game and the Week 5 (link) Rams at Seahawks game are tied as the most back and forth games, with the Week 14 thriller between San Francisco and New Orleans (link) right behind. And although it wasn’t as high scoring as those previous contests across the entirety of the game, Chicago’s win in Week 2 over Denver featured a flurry of changes near the end. In the final two minutes, there were five plays — a Denver fourth down conversion, Denver touchdown, Denver two-point conversion, Chicago completion into field goal territory, and a Chicago game-winning field goal — that swung each team’s chance of winning the game by at least 25%; no game to date has had more than three such plays.