After my first article on expected points added (EPA) I wanted to look into if EPA differed depending on where the play was happening on the field. This could be important to know as it can help a team decide on when it wants to me more or less aggressive, based solely on field position.
Every graphic in this article has “Yardline” as its x axis, this is the location on the field and ranges from 0 to 100. Think of this as the way the team is going, so 0 would be the team’s own end zone, if a team were to get a touchback they would get the ball on the 25-yard line, the 50 is midfield, the red zone starts at 80, and the opponent’s end zone would be at 100. As with the last article, all data is from the 2019 regular season.
The first graphic shows the average EPA per pass attempt by yard line. A moving average line of 5 yards before and 5 yards after is shown to better display what the average is at any given spot on the field. Additionally, the red zone has been shaded on the right side for reference.
There are two peaks and a trough in the graphic. The first peak occurs right outside of a team’s own end zone at around the 10 yard line. The second happens in the red zone at about the 90 yard line and continues to the 97 yard line. The trough bottoms out at the 32 yard line.
A lot of this is intuitive and makes sense. The first peak happens quickly when teams are trying to get out of being backed up on the field, lots of explosive plays can happen at this spot on the field. The trough happens at the 32 yard line which is a few yards after the touchback yard line. The trough happening here would indicate a lot of thwarted drives, which is reasonable.
The final peak occurs in the red zone. Of course most scores happen after teams get in the red zone, and more often than not would happen when the offense is within ten yards of the end zone.
The second graphic shows the average EPA per rush attempt per yard line. A moving average line and red zone shade has been added as well.
Rush attempts only has one peak and one trough. From the beginning the moving average dives to the 34 yard line where it then picks up to the peak at the 86 yard line where it then falls again.
What’s interesting is the EPA dive in the end zone with rush attempts. This decline is for all the goal line stands defenses put up when other teams try to run the ball into the end zone.
The third graphic is a simple combination on the two moving average lines to properly compare the two.
The biggest take away from this comparison is how much higher the EPA per pass attempt peak is in the red zone compared to the rushing line. The troughs for both lines are just about at the same level and at the same location.
The final two graphics look at EPA per pass and rush attempt by team in the red zone.
The Baltimore Ravens, Minnesota Vikings, and Tennessee Titans are the best teams by this measure in pass attempts. The Ravens fall off around the 90 yard line while the Titans pick up right around the 90 yard line.
The Tampa Bay Buccaneers are just bad by this measure. They trade places in a few spots with the Washington Redskins as the worst team in the redzone.
The Kansas City Chiefs have a clear advantage when it comes to rush attempts in the red zone. They are almost a whole point above the next team at the 97 yard line and about a half point above the next best team from the 85 to 96 yard line.
The Los Angeles Chargers, Indianapolis Colts, and Miami Dolphins are the worst teams by this measure.
Knowing where teams succeed or fail on the field based on EPA can be advantageous to not only defenses, but also the teams themselves. Take for example the Kansas City Chiefs in rush attempts. If defenses knew the Chiefs are above average rushing in those locations on the field they could play a much more run heavy defense in those positions. Of course, if they Chiefs knew they were above average in this area of the field they may intentionally pass the ball based on what the defense shows.
Data: https://www.rdocumentation.org/packages/nflscrapR/versions/1.4.0
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