By: Arnav Saxena
Introduction
In the 2020 NFL season, Tennessee Titans running back Derrick Henry finished with 2,027 rushing yards, just 79 yards short of breaking the thirty-six year old rushing record set by Los Angeles Rams legend Eric Dickerson. Two years prior, Pittsburgh Steelers quarterback Ben Roethlisberger threw for 5,129 yards, 349 yards away from breaking Peyton Manning’s single-season passing yards record. Over the course of recent NFL history, many players have come close to breaking long-lasting single season records, but fall short for one reason or another, an annual reminder of how impressive some of these records are.
However, the 2021 NFL season changed the landscape for single-season records. Before the year, NFL owners voted in approval of a 17 game regular season, an expansion from the traditional 16 games, at the Annual League Meeting. The introduction of an additional game not only provides fans with an extra interconference matchup for each team, but also gives players an opportunity to record an extra game’s worth of statistics, making various NFL records vulnerable. You have to believe if you gave Derrick Henry an extra game last year he almost certainly would’ve broken Eric Dickerson’s record. In this article, I will explore what NFL records are at the greatest risk of being broken upon the introduction of the 17 game season, using data from the last five NFL seasons to analyze various offensive and defensive records and the probability that they are broken over one-year and five-year periods.
The data used for the study all comes from Pro Football Reference. For each category, I pulled the league leader’s data for each of the last five seasons. I created a distribution for each season based on the 16 games of data. After plotting the distributions, most were bell shaped, so it was appropriate to use z-scores, a standardized measure of how far above or below a certain value is from the mean. After calculating the mean and standard deviation for each season, as well as how far away the player was from breaking the record, I could calculate the z-score of the statistic needed to break the record. Based on the z-score, I could find a p-value for each season-- the probability that the given player would break the record in an extra game. Thus, it was an effective model for predicting the likelihood of a player breaking the record if they were given an extra game-- if the NFL season was 17 games long instead of 16. For example, Derrick Henry had 2,027 rushing yards in 2020, averaging almost 127 yards per game with a standard deviation of 59 yards. He would have needed 79 yards in a 17th NFL game to break the record, which has a z-score of (79-127)/59 = -0.81, giving him a 79% chance of breaking the NFL single-season rushing record in a 17 game season.
After calculating the p-values for each player from each season, I calculated the one year and five year probabilities of the records breaking. The one year likelihood was taken by averaging the five p-values for each record, giving an average probability of a player breaking the record in a year. For example, the p-values for breaking the passing yards record for 2016-2020 were 0.796, 0, 0.338, 0.283, and 0.001, so the one year probability would be 0.284, or a 28.4% chance that the passing yards record is broken each year. The five year span probability was calculated by taking the complement of the chance that none of the players across the five seasons break the record, so for the same passing yards record example, the probability that the record is broken in five years would be 1 - ((0.204) * (1) * (0.662) * (0.717) * (0.999)) = 0.9034, or a 90.34% chance that the passing record falls in five years.
Passing Records
As the league became more quarterback-centric, with passing becoming more common on first and second downs and rules protecting the quarterback more than ever before, passing records were already at some risk before the season expansion. Over the last five seasons, Drew Brees was the closest to breaking the passing yards record set by Peyton Manning, just 270 yards short of setting a new mark in 2016. Since he was averaging 325 yards per game, the model predicts that he had a 79.6% chance of breaking the record if he was given one more game. As shown in the computations above, the probability of the passing yards record being broken in one given year is 28.4%, while the chance that it is broken over the course of five years is 90.34%, which is shown in the graphs below.
Looking at the graphs, we can see that passing touchdowns are much less likely to be broken over the course of five years. Patrick Mahomes came the closest to breaking the record in 2018 when he tossed 50 touchdowns in his MVP season, but was still 6 touchdowns short of breaking the record set by Peyton Manning in 2013. The model gave him around a 4% chance of achieving this, but all the other quarterbacks in the five years had a negligible chance of breaking the record, explaining why the probability of the passing touchdowns record breaking over 5 years was only 4%, and the probability of the record breaking in one year was just 0.7%.
Rushing Records
The rushing records in the NFL felt almost impossible to break until Derrick Henry was within 80 yards of besting Eric Dickerson’s mark. In fact, the next closest running back over the last five years besides Henry was Ezekiel Elliott, who was 476 yards off the mark, and even though he was rushing for over 100 yards per game in the 2016 season, the model gave him a 0% chance of breaking the record given an extra game. As a result, the only non-zero p-value comes from Derrick Henry at 0.785, meaning that he was the sole influence for the one and five year spans, with the five year probability simply equaling his single season p-value at 0.785 and the one year probability being his p-value divided by 5, or 0.157. By inspection, it becomes clear that Derrick Henry might have had an outlier season for rushing yards in 2020-- even this year before his injury, he was not on pace to beat his own personal mark. As a result, we must treat the model’s predictions with a bit of caution and say that the right-lying outlier skewed the model’s predictions right.
Examining the rushing touchdowns record and the last five seasons of rushing touchdown data makes LaDainian Tomlinson’s 2006 record of 28 rushing touchdowns all the more impressive. LeGarrette Blount of the 2016 Super Bowl champion New England Patriots came the closest over the last five years, rushing for 18 touchdowns over the course of the year. Even though he was rushing for more than one touchdown per game, the model gives him a 0% chance of rushing for 11 touchdowns to break the record in a 17th game. Thus, everyone had a p-value of 0 for each of the five seasons, making the probability zero for both the one and five year spans. As the NFL moves away from running the football and has evolved greatly in the passing game, it feels like the model is correct in predicting that LaDainian Tomlinson’s record is unbreakable, and unless there is an outlier like 2020 Derrick Henry, the rushing records might stand the test of time.
Receiving Records
As passing records continue to fall in the NFL, one might think that receiving records are next. As recently as 2019, Michael Thomas set the new record for most catches in a single season, pulling in 149 balls, beating Marvin Harrison’s previous record of 143 catches in 2002. However, the single season receiving records for both yards and touchdowns are some of the most legendary marks in NFL history. Calvin Johnson had 1,964 receiving yards in the 2012 season, and the next closest player is almost 100 yards away from that. Even Michael Thomas’s record setting year had him 240 yards shy of breaking the record, for which the model gives him a 0.03% chance of doing in an extra game. He was the closest to breaking the record over the last five years, and although some other receivers had non-zero p-values, the five year probability was only 0.0004, while the one year probability was 0.00007.
Randy Moss catching 23 touchdown passes in 2007 might be even more impressive than Calvin Johnson’s record, as the only other player in NFL history to catch more than 20 touchdowns in a year is the legendary Jerry Rice. Davante Adams came the closest to breaking the record over the last five years when he recorded 18 touchdown grabs in 2020. In fact, he holds the third spot for receiving touchdowns in a season behind Moss and Rice. Despite his first-team All-Pro season, the model only gives him a 0.0001% chance of catching 6 touchdowns in a 17th game, the number needed to break the record. The rest of the receivers over the five years of data all had p-values of 0, so the probabilities for the one and five year spans are only influenced by Davante Adams, and even then, the five year probability is 0.000001 and the one year probability is practically 0. Even in outlier seasons like Michael Thomas’s 2019 campaign or Davante Adams in 2020, the odds of the receiving records breaking are close to 0, indicating that the receiving records might be untouchable as well. Even though the league evolves into a more pass-heavy game, running backs and tight ends continue to get expanded roles in the passing attack, indicating that Calvin Johnson and Randy Moss might hold these receiving records for years to come.
Defensive Records
Defensive records are often forgotten just because of how high-powered offenses have become in the NFL. Michael Strahan set the mark for sacks in 2021, getting to the quarterback 22.5 times during the season, while Dick “Night Train” Lane’s 14 interceptions in 1952 has been the single-season record for almost 70 years. As quarterbacks get more accurate and interceptions in general are decreasing, it seems like this record is almost unbreakable. The closest player in the last five years was Xavien Howard in 2020, recording 10 interceptions. Needing 5 interceptions in a 17th game, the model gives him a 0% chance of doing so, along with all the other interception leaders from the last five years. As a result, both the one and five year probabilities are 0, suggesting that this record will never be broken. However, at the time this article was written, Trevon Diggs of the Dallas Cowboys picked off 8 passes over the course of just 9 games, or a rate of 0.88 interceptions per game. He needs 7 interceptions over the next 8 games to break the record, or a rate of 0.875. The model gives Diggs a 52.1% chance of breaking the record, although it has fallen from the 77.7% chance it gave him earlier in Week 6. It seems like it would take a great outlier like Diggs to even come close to touching Night Train Lane’s mark.
On the other hand, we’ve seen several sack masters emerge over the last few years in the NFL. In 2018, Aaron Donald recorded 20.5 sacks, needing just 2.5 sacks to break Strahan’s record. The model gives Donald a 16.75% chance of recording this mark, and gives two other players non-zero chances of breaking the record given a 17th game. Subsequently, the five year probability is 0.1911 and the one year probability is 0.039. It would certainly take an incredible season to break the record, but it’s not completely out of the question that the sacks record will fall given the expanded schedule.
Conclusion
After analyzing the various records, the ones most likely to be broken in the next five years because of the expanded NFL season are passing yards, sacks, and passing touchdowns. The passing yards mark has a 90.3% chance of being broken over the next five years, while passing touchdowns is just over 3%. This can be explained by the NFL’s improved quarterback play over time and the rise of young offensive-minded coaches in the league, resulting in ludicrous quarterback stat lines. Michael Strahan’s sack record has a 19.1% chance of being broken in the next five years. Records like rushing yards or interceptions had an outlier in Derrick Henry and Trevon Diggs greatly influencing the chance they’d be broken, but are realistically unlikely to break. Other records had almost zero chance of breaking, illustrating how remarkable some of these record-setting seasons truly are. Perhaps it will be a while before an NFL record is broken, but the introduction of a 17th game to the regular season adds a bit more excitement to the end of the season for NFL fans and players alike.