Evaluating Quarterback Efficiency, Using Heatmap Plots
By: Christopher Zita
Tags: Data Science, Sports, Heatmap, Analytics, NFL

NFL quarterbacks are the most analyzed position in all of sports, as team success greatly correlates with quarterback performance. Important quarterback statistics that are often viewed to indicate performance is touchdowns thrown, completion percentage, and interceptions thrown.

What these stats often don’t show though is where on the field the quarterback is the most accurate, least accurate, and where the ball is thrown the most.

This is where the help of heatmaps come in place. By using the heatmaps in the seaborn library in python and web scraping the play-by-play data from Pro-Football-Reference, we can create a Quarterback Heatmap Plot (QMP) that indicates where on the football field the ball is thrown the most, and how accurate the quarterback is in that specific area.

Quarterback Heatmap Plot

The plot on the left is the Quarterback Heatmap Plot of Russel Wilson for the 2019 season. It shows that on the short left hand side of the field for passes 15 yards and under, this is where he throws the ball the most with a completion percentage in this area of about 70%. But we can actually see he is much more accurate in the short middle of the field with a outstanding completion percentage of 81%. When it comes to throwing deep he again throws more often to the left hand side of the field but with a much lower completion percentage of only 43%.

From viewing this plot we can now go deeper into evaluating Russel Wilsons performance for the 2019 season. We saw that he is much better at throwing the ball short rather than long, but what is interesting is that he tends to prefer throwing to the left hand side of the field even though he throws with his right. This is difficult for some quarterbacks because this means you have to throw across your body but it seems Russel Wilson prefers it.

The discoveries being made gave us a more in depth look at Russel Wilson that we wouldn’t have known by just looking at his basic statistics. But now the question is what can we do with this new found information?

Applications

By using these plots and getting much more information on the quarterbacks and where they throw, this info can be made useful in a number of ways. Some examples of these are:

1. Coaches

Coaches can use this info to game plan for a specific quarterback. If they see a quarterback has a specific area of the field they like to throw too and are accurate, a coach may put more defensive players covering in this area to make the quarterback throw elsewhere. On the other side if they see an area where the quarterback is significantly less accurate than others, the coach may decide to put less defenders in that area or blitz players on that side so the quarterback is encouraged to throw on that side/area of the field.

The play above is a cornerback blitz on the left side, the result will be less men covering on the left side of the field than the right, encouraging the quarterback to throw to the left

2. Fantasy Football Players

In fantasy football picking a quarterback you believe will have a good performance on Sunday is crucial to winning pools and prizes. An example on how you can incorporate this info to increase your chances in winning in these pools is by looking at the areas the quarterback throws the most and looking at the cornerbacks defending in those areas on the opposing team.

Above: Stephon Gilmore

For example, Stephon Gilmore of the Patriots has been the best corner in the league this year and usually plays on the right hand side of the field. Now if the quarterback you want to choose for this week is versing the Patriots and he throws mostly to the right hand side, it may be wise to choose a different quarterback. This is because with a shutdown corner like Stephon Gilmore, that quarterbacks performance is most likely to decrease from his usual standard.

3. Comparisons

Pro-Football-Reference is a great site for football statistics because they have play-by-play databases for quarterbacks from the last 10 years. This means we can create a Quarterback Heatmap Plot for any quarterback who has played in the last 10 years. And by doing this we can compare different quarterbacks from different years, or the same quarterback from different years to see if they are improving or declining.

As an example we are going to compare the stats and performances of 3 quarterbacks of the last decade who have won MVP, and show their Quarterback Heatmap Plot for that respective year.