Each week we’ll highlight a few of the most important coaching decisions that contributed heavily to the final result. While many of these high leverage situations occur on fourth down, we’ll introduce some other situations where a coaching decision swung his team’s chances of winning in a major way as the season goes on.
There are a few main tools for doing this analysis: The most obvious is win probability, which takes into account the situational components of the game along with the strength of each team in each facet to predict the chance of winning. Another data point that is useful and in most cases, aligned with win probability is expected points, which takes into account the field position, down and distance to predict the number of points that we expect the offense to score on the next offensive play. We can also compare the expected points for a team before and after a play to measure how successful a play was, and we’ll also make use of conversion probability, which leverages the strength of each team in each facet to predict the chance a team picks up a first down on a given play.
During the season, more analysis may work its way into this column, but this gives us plenty to start with. While we leverage machine learning to make sound predictions for each of the above, we will do our best to make this article accessible to all and we’ll do our best to answer any questions.
Bill O’Brien: 4th-and-3 at Kansas City's 27, up 31-24 with 2:00 to go in the fourth quarter
The Houston Texans, with a 31-24 lead, faced a fourth down and three yards to go against the Kansas City Chiefs in Arrowhead; three yards to go to a sure victory on the road as a decided underdog to Super Bowl hopefuls and reigning MVP Patrick Mahomes. After a two-yard loss on third down led into the two-minute warning, Houston, at the Chiefs 27-yard line, went for the first down and the sure win instead of attempting a 45-yard field goal that would have made it a two-score game but would not have wrapped up the victory.
Our models, powered by the machine learning capabilities of the AWS Cloud, gave the Texans a 60% chance of converting the fourth down, which would give them a 100% chance of then winning the game (the Chiefs had no timeouts remaining). Their chance of winning upon the attempt of a field goal was 92% (there was a 72% chance to make such a field goal attempt), and if they were stopped, it would have resulted in an 84% chance to win for Houston.
Patrick Mahomes and the Chiefs were having a bad day, scoring just 17 points after a miraculous catch by Tyreek Hill in the opening minutes of the game. However, Bill O’Brien surely realized that you do not want to over exaggerate to a small sample. Instead, he considered the large amount of data that tells you that the Chiefs are the best offense in the NFL and Mahomes is probably the last quarterback you want to give even a sliver of daylight to. The Chiefs' defense has been an issue for the last two seasons, and BOB made the shrewd decision that his best chance of winning was by putting the ball in the hands of 2019 MVP candidate Deshaun Watson.
The Texans went to their best receiver and completed an eight-yard pass to DeAndre Hopkins, effectively ending the game and significantly altering the playoff picture in the AFC. With the win, the Houston quadrupled their chance to earn a first-round bye in the AFC playoffs, while effectively cutting the Chiefs’ in half. No team has made the Super Bowl without a bye since the 2012 Baltimore Ravens. This was the week’s best game, and it also delivered the week’s best decision.