By Brian Reiff

The Patriots are again one of the NFL’s top teams. Not something that’s surprising to anyone, but the way in which they’re doing it has made headlines.

The Patriots’ defense has been other-worldly this season, ranking first by an assortment of metrics: points allowed, yards per play, total yards allowed (among teams that have played six games), turnovers forced, Adjusted Net Yards per Attempt (ANY/A), and pretty much any other stat you can find on Pro-Football Reference. In fact, the Patriots are so good that they’re actually forcing turnovers on a higher percentage of drives (20%) than they’re allowing the opposing team to score (6%).

Even when looking at more advanced metrics, the Patriots still come out on top. A good way to measure performance is through Expected Points, specifically looking at Expected Points Added (EPA) per 60 plays. By this metric, the Patriots have still been the top defense, but their gap at the top is narrower than some might’ve thought.

2019 EPA Allowed Per 60 Plays Leaders

A negative number here is good for the defense, indicating the offense was losing an average of 22.2 Expected Points every time they ran a game’s worth of plays against the Patriots defense. However, the 49ers are right there with them, with both enjoying a large lead over the rest of the league.

However, there is still a notable factor being left out of this analysis. The Patriots have played one of the easiest schedules in the league, feasting on the likes of the Steelers (2-4), Dolphins (0-5), Jets (1-4), Redskins (1-5) and Giants (2-4). Has their defense actually been as good as the number show, or have they just played bad teams that have inflated their numbers?

To determine this, we can look at what the Patriots’ opponents have done in their games against teams other than the Patriots.

For example, the Jets averaged -28.8 EPA per 60 plays against the Patriots, but they’ve averaged -15.0 EPA per 60 plays in the rest of their games against the Bills, Browns, Eagles and Cowboys. With those numbers, we could say that the Patriots were 13.8 points better than an “average” team was against the Jets (the Jets have likely not played an exactly “average” schedule, but in the aggregate among all teams it should be close enough).

All of the Patriots’ opponents this season have combined to average -5.4 EPA per 60 plays in their games against teams that weren’t the Patriots, which ends up being the second-lowest mark by a team (the Cowboys’ opponents have averaged -7.2 EPA per 60 plays). If we take the Patriots’ overall number (-22.2) and compare it against their opponents’ average (-5.4), we see that the Patriots’ defense was 16.8 points better than an average team. Doing this for all teams, we can produce an opponent-adjusted leaderboard that should provide a better answer to the question of which defense has reigned supreme in the NFL so far this season.

2019 EPA Allowed Per 60 Plays Leaders
Adjusted for Opponent

Three of the top five teams remain the same, but there is a new leader—the San Francisco 49ers. After adjusting for the teams they’ve played, the 49ers have actually stifled their opponents more so than the Patriots, despite trailing behind them in the raw numbers (albeit slightly). The Patriots are a close second, so it’d be improper to say their defense hasn’t been great. However, it’s clear that the two teams comprise a top-two rather than the Patriots sitting alone at the top.

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