According to the NFL, the New England Patriots were found to have introduced 11 under inflated footballs of the 12 they were required to provide during Sunday’s AFC Championship game vs the Colts. The footballs were said to be underinflated by two pounds per square inch. The incentive to having the Patriots offense play with underinflated footballs is that they are easier to grip, throw and catch as compared to properly inflated footballs.
Naturally, the immediate question arises: “How long have the Patriots been playing with underinflated footballs?” That’s impossible to know, but if the Patriots and Tom Brady believed it was to their advantage to underinflate the footballs for easier grip, presumably they would be doing it in wet weather, much like the weather in New England for the game vs the Colts.
I went through all NFL game books for the Patriots home games since the 2005 season. What I found was, at a minimum, intriguing. The game books list the “game weather”. First, the data I share below assumes this weather report is at least somewhat accurate. I did go back and cross reference every game vs historical daily weather reports for the area. That said, its possible one or two additional games should be added in case the game book reported clear conditions when it was, in fact, wet.
Second, I presumed that Tom Brady, the quarterback, was the primary individual who would benefit most from underinflated footballs, so I excluded the 2008 season when he did not play due to injury suffered in week 1. I won’t speculate as to whether the direction to underinflate the football was given by Brady or not, but I simply removed games he did not start.
The first table below shows the Patriots performance in wet weather in a game by game basis. After the Patriots suffered losses in their only two home wet weather games in 2006, a strange phenomenon occurred:
The Patriots went 14-1 (93%) in Tom Brady’s home games played in wet weather since 2007. Their only loss was to the San Francisco 49ers in 2012. For some comparison, the Patriots went 51-9 (85%) in home games played in dry weather during that same period. On average, in both wet and dry weather, the Patriots were favored by approximately 9 ppg. In the NFL, 9 point favorites should win the game approximately 81% of the time.
As you can see from the averages at the bottom, Tom Brady put up remarkably similar numbers in wet weather as he did in dry weather: 7.4 yds/att vs 7.6 yds/att, a 99 passer rtg vs 101 passer rtg, and a slightly better TD:INT ratio in wet weather as compared to dry weather.
The second table (below) looks more in depth at the results of those 15 wet weather home games since 2007 as compared to the Patriots performance in dry weather home games. The compared results are strikingly different:
The Patriots went 31-29 ATS (52%) in dry weather home games, but 10-5 ATS (67%) in wet weather home games. The oddsmakers on the games projected the Patriots would score an average of 28 ppg, whether the conditions were wet or dry. But the Patriots scored 35 ppg in wet weather (+7) vs 31 ppg in dry weather. They also held opponents to 5 ppg fewer in wet weather home games.
Thus, their average win improved from 30.7-19.6 to 34.6-14.3. In other words, they went from winning games by 11 points to winning by over 20 points on average, despite being favored by 9 ppg in both scenarios.
This analysis does not prove or disprove anything. It certainly may fuel the fire of conspiracy theorists, but without any concrete evidence that the Patriots were underinflating footballs for Tom Brady in wet weather, we can only look at the game results. While obviously suspicious, despite how strongly it appears “something” is helping the Patriots in wet weather, nothing can be proven by this study.
I always watched the Patriots and saw how they performed in wet weather. Anecdotally it seemed like they “got it”: they knew the pass rush was slower and while other teams shifted AWAY from the pass and to more ground based games in the wet weather, it seemed the Patriots shifted the opposite direction, and passed the ball more frequently. I always thought this was just “Bill Belichick and Tom Brady being smart and ahead of the game”. Perhaps that is still the case. Or perhaps they passed more because their offense played with underinflated footballs in wet weather while their opponent played with regulation footballs. Its total speculation. I am of the opinion that we will never know. This whole allegation could be a lot of hot air. I am not opining on what happened, whether other teams do it too, the level of advantage which is gained, etc. I am simply providing actual data on game results and letting you use the data in conjunction with news/media reports to form your own conclusions.