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. 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.
The decision of the week
Just like playing in the NFL, coaching in the NFL also comes with a learning curve. Flashback to Kliff Kingsbury’s first game as a head coach in pro football four weeks ago: Down 0-17 late in the first half, his Arizona Cardinals knocked on the door for the first time but came up short on three downs and faced fourth-and-goal from the two-yard line. Just one week later, against the Baltimore Ravens, they faced fourth-and-one at Baltimore’s four-yard line down 0-7, and later in the game again, they faced fourth-and-goal from the two-yard line while trailing by 11 points. What do all these situations have in common? In all three situations, the math would have told him to go for it on fourth down, and in all three situations, Kliff Kingsbury opted to kick the chip-shot field goal, denying his team the chance to put up more points in games that ultimately ended in a tie and a one-score loss, respectively.
Fourth time’s a charm, as the Cardinals found themselves in a similar situation yesterday. Yet, not much had happened on the scoreboard this time, as the Bengals were only leading 3-0, and after moving 62 yards down the field, the Cardinals found themselves in a fourth-and-two situation at Cincinnati’s six-yard line with 3:40 to play in the first quarter. This time, Kliff Kingsbury was either fed up with chip-shot field goals, or he had someone perform the following computation for him in the last three weeks.
If the Cardinals convert in this situation via a two-yard gain, their chance to score a touchdown jumps up to 76%. Of course, the actual value of a potential conversion is even higher, since many conversions would come with a greater gain or even an immediate touchdown. But what if they fail? That’s not the end of the world, either. If they are stuffed for no gain or throw an incomplete pass, the Bengals take over on their own six-yard line. The numbers suggest that the Cardinals would still be more likely to get the next score in the game, as that would happen 55% of the time. The Bengals' possession would, in fact, be worth negative expected points.
Add that the Cardinals had a 56.7% chance of converting the attempt per our model, which estimates their chances based on historical conversion rates and the respective unit strengths, and it’s not surprising that this is a good time to be aggressive. Adding it all up, our expected points model says that a fourth-and-two attempt in this situation is worth 4.4 points. This is obviously more than a field goal, so we don’t have to bother with the field goal percentage of a 24-yard try. Instead, we applaud Kliff Kingsbury for the good decision.
Maybe even more impressive than the correct decision was the play that followed, taking advantage of Kyler Murray’s unique skill set. They came out in 12 personnel, lining up the tight ends next to each tackle. They also brought in Trent Sherfield as a run-blocker via motion, leaving KeeSean Johnson on the right side as the only outside receiver in a heavy formation. Of course, Johnson was matched by a cornerback, but other than that, the Bengals sold out to stop the run, putting nine defenders in the box and positioning a safety in the middle of the endzone, and this rendered the left side of the field vacant. With eight players run-blocking over the middle, the defense reacted to the following fake handoff, and Kyler Murray’s bootleg to the left made it across the line to gain untouched. The fact that he also made it past the only would-be tackler for the touchdown was the icing on the cake on what goes down as the PFF Decision of the Week.
The Decision that wasn’t
The Seattle Seahawks prevailed at CenturyLink Field Thursday night, winning a one-point affair 30-29 after Los Angeles Rams kicker Greg Zuerlein missed a 44-yard field goal with less than a minute left. It was a back-and-forth affair that might not have needed to be. With 1:38 remaining in the second quarter, the Seahawks — after forcing the Rams to take a timeout, and taking one of their own — missed a 48-yard field goal on fourth-and-one. The Rams then took the ball and marched it down the field for a Cooper Kupp touchdown to cut the Seahawks’ lead to 14-13 as they headed into intermission.
This is an example of a situation where the decision was bad at first blush, and the worst results followed for the Seahawks as a result. Not only were the benefits of converting the fourth down higher than those from converting the field goal, the conversion rate of the former (70%) actually exceeds the latter (65%).
If the Seahawks converted the fourth down, their chance of winning the game would have been 81%, versus 68% had they been stopped. In attempting the field goal, they assumed a 73% chance of winning the game. All of this assumes what we know about Seattle, which is that they have one of the best quarterbacks in the league and a running back in Chris Carson that was difficult to stop all night.
In a results-driven league, hopefully, the existence of a positive result Thursday will not keep Seattle from learning from the fact that they opened the door wide open for a Rams team that they had completely controlled for almost the entirety of the game’s first half.