A guide to modern football analytics for beginners
The term “analytics” may be the most polarizing word in all of football among fans, pundits and even members of the NFL, as it has become more popular throughout the league in recent years.
Many people reanalyze sports geeks on a spreadsheet and scoff at the idea that NFL decision makers can make critical personal decisions about a game or player based on a mathematical equation.
Analytics is a broad term that does not necessarily explain the differences between metrics that are becoming more and more common in football analysis these days. Most “math” haters deal with predictive analytics or winning probability models that tell NFL coaches that they should run, chase a goal, or shoot a field goal in certain situations.
However, there is another world in football statistics that I will use most often on Patriots.com: score-based stats. Like yardage, points, or passer rating, there are no predictive qualities for these stats that are invented by what happened, in the past tense, on the field.
The point of these metrics is to provide more context in player rating and team efficiency than the traditional raw stats you’ll see in the points box. For example, there is a significant difference between an offense gaining two rushing yards at the third and ten and two yards in the third and one. One run led directly to a fourth down (and potentially a field goal or target), while the other moved the strings for a new set of touchdowns.
We’ve all heard telecasts for years say Team X is 10-0 when they rush over 100 yards as a team. Well, duh, when NFL teams have a late lead in games, they’re going to run football to take advantage of the clock, so rushing yards pile up. Along the same lines, we all remember back in Week 7 when the Seahawks blasted the Chargers 37-23, but you lost in fantasy football because Austin Eckler scored a touchdown in trash time. Was this just me? Oh, okay.
Don’t take anything from Ekeler, but those trash time yards and landings when the game is already decided shouldn’t count like yards and landings in a close game.
Furthermore, scoring or moving the ball against an upper defense should be more favorably weighted than scoring against a 32nd-ranked NFL defense and vice versa. If the end goal is to analyze the difference with as much information as possible, then the prime numbers are not.
This is where up-to-date football stats and metrics, such as Defensive Peripheral Value (DVOA) and Points Added (EPA), can help tell the whole story.
As you can find on the Football Outsiders website, “DVOA measures a team’s efficiency by comparing success in each match to the league average based on position and opponent.”
To get back to our examples, traditional stats like yards per carry that calculate a two-yard run for third down the same. It’s two yards, be it third and long or third and short. DVOA, on the other hand, stands for down and distance. It also weighs the opponent, so if the Patriots lunge for 200 yards against a sixth-ranked Buffalo defense, that gives the Pats more credit than dashing for the same amount of yards against a last-placed Houston defense.
The expected points added are similar by taking into account the bottom, distance and field position to determine how many points a player or playing team is worth. Like the DVOA, the EPA uses a baseline average of yardage typically earned in a given game situation to “measure how well a team is doing relative to expectations.”
Although they are slightly different, the idea behind them is the same, which is to provide context for each game based on the state of the game for a more accurate ranking of players and teams.
Just because these scales are new and admittedly a little dumb doesn’t mean they are bad. In fact, they make us all smarter as analysts and football fans than old school stats.
Here are some of the other metrics we’ll be using here at Patriots.com with a quick explanation of each:
Success rate:Like DVOA and EPA, the pass rate is the calculation of a playing result based on distance traveled. Typically, thresholds gain 40% of the required yards in the first descent, 60% of the required yards in the second down, or 100% of the required yards in third and fourth (via Football Outsiders). This metric is a good way of calculating offensive or defensive efficiency in early touchdowns (example: bats have an early success rate of only 37% against planes in week 8. Third and long with an average distance to travel of 9.2 yards, resulting in a conversion rate third down at just 31.6%).
Completion rate over expected (CPOE):CPOE understands that not all completions by quarterback are created equal. The meter calculates the probability of a complete pass based on several factors such as field position, bottom line, air yards, yards to be cut, passing position, and whether the midfielder is under pressure. From there, we can break down the difficulty level to complete an NFL game (example: Mac Jones completed a five-yard check on the first down versus a 15-yard crossover on the third and 12).
– aDOT (Average Depth of Target): its very easy. It’s the average air distance a pass travels divided by the number of pass attempts (example: Mac Jones didn’t push the ball down much against the Colts last week, with aDOT only 5.5 yards).
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