With the success the Patriots have enjoyed over the last 20 years, it makes sense that teams around the NFL would want to follow their blueprint. So after New England won a Super Bowl while leaning heavily on its run game out of two-back, one-tight end sets (21 personnel), the logical conclusion is that teams would combat smaller defenses better equipped to stop spread offenses by going back to bigger personnel groupings that include fullbacks and tight ends.

We’ve heard that nearly every offseason over the past few years and that didn’t change in 2019. Here’s an excerpt from Sports Illustrated’s Albert Breer, predicting a return to heavy run packages … and also a tweet calling out the passage for being wrong, which it is.

Wish this was April Fools and not the consensus among NFL media. Throwing the ball isn't rising because of being equated with creativity. It's about scoring more points pic.twitter.com/UKuQlqILdi — Kevin Cole (@KevinColePFF) April 1, 2019

An NFL team building its roster to mimic the Patriots’ two-back offense is foolish for two reasons:

(1) New England’s offense is always evolving.

The Pats essentially created the slot receiver position as the NFL knows it back in 2007 with Wes Welker, and every other team in the league followed suit. A few years later, the Patriots moved on to 12 personnel (one running back, two tight ends) with Rob Gronkowski and Aaron Hernandez filling the starring roles. And now, New England’s offense is viewed as a throwback and one of the few that regularly uses a fullback.

So, sure, copy whatever the Patriots are doing right now; it’s probably going to change next year and you’ll be left behind.

Also…

(2) The Patriots did not win in 2018 BECAUSE of their high usage of two-back sets; they won IN SPITE of it.

If an NFL team wants to learn how to design a good offense that bases out of 21 personnel, it shouldn’t be studying New England. It should be studying Kyle Shanahan’s offense in San Francisco. The 49ers averaged 0.4 Expected Points Added per rushing attempt and 0.12 points per drop back out of 21 personnel, according to Sports Info Solutions. The Patriots averaged -0.06 EPA per rushing attempt and just 0.01 points on pass drops.

Passing… SF: 0.12 EPA/dropback

NE: 0.01 EPA/dropback — Steven Ruiz (@theStevenRuiz) June 11, 2019

(And, no, these numbers weren’t deflated by the Patriots running out the clock late in wins. Their first-half runs out of 21 personnel were even less efficient at -0.023 EPA/attempt.)

So if an NFL team’s takeaway from New England’s Super Bowl run was to sign a fullback and use bigger personnel groupings and run the ball more — that’s what Bill Belichick did, so it must be right! — it’s not paying attention.

But here’s where there’s a disconnect between the X’s and O’s people and the analytics community, which might take these numbers and say the Patriots should have completely abolished their 21 personnel sets: Those runs out of 21 personnel may not have been efficient but they did set up other (more fruitful) aspects of the Patriots offense late in the season.

Calm down, nerds. I already know what you’re thinking: There’s no evidence suggesting that running success (or volume) has any effect on a team’s play-action passing game, which is true. Linebackers aren’t thinking about how many runs they’ve seen or how successful a team’s running game has been when deciding whether or not to bite on a play-fake. They are reading their keys and making a decision based on that.

But …

With FB James Develin in the backfield, performing a number of actions — iso blocks, kick-out blocks, wham blocks, etc. — thanks to the Patriots’ diverse run scheme, opposing linebackers had a much more difficult time diagnosing what was going on in front of them. And linebackers are coached to take on those iso and wham blocks with a more aggressive approach. They’re instructed to beat linemen climbing up to the second level in order to clog interior run gaps and “spill” those runs outside. Adding those backfield actions to the play-action passing game should do a better job of occupying the linebackers and creating space between the second and third level of the defense.

Here’s two clips. The first shows the Jets’ weakside linebacker correctly reading the fullback and attacking the line of scrimmage (though failing to shed a block and make the play). The second shows a Pittsburgh linebacker making a similar read, because the play looks very similar … right up until Brady pulls the ball and looks to pass, causing the linebacker to be late in his drop toward the middle of the field. Tom Brady exploits the opening immediately.

Even the nerds will concede that spacing is the key to the play-action game, and, in theory, the backfield actions that are only possible out of two-back sets create that space most effectively.

It shouldn’t come as a surprise that after the Patriots made 21 personnel the foundation of their offense in Week 12, their play-action passing game took off. While it was productive during the first 11 weeks of the season (0.31 EPA/dropback); it was pretty much unstoppable over those last six games, producing 0.56 expected points added per dropback. For a team that was struggling to produce explosive plays in the passing game, the play-action pass out of 21 personnel provided a much-needed boost. Tom Brady averaged over 11 yards per attempt on those plays.

The other added benefit of running out of 21 personnel was that teams were more willing to match the grouping with base defense, which would spark New England’s no-huddle attack. Brady’s passes produced 0.14 expected points added per dropback throughout the 2018 season. That number jumped to 0.24 on “no huddle” passes out of 21 personnel.

So, yes, the high usage of 21 personnel benefitted New England in ways that might not show up when doing a surface-level statistical analysis of the Patriots offense. But it’s still worth asking if those benefits outweighed all of the inefficient play-calls that made them possible.

The correct answer is probably “no,” but none of this really matters, because it’s unlikely that we’ll see New England commit to this strategy long-term. The Patriots signed new TEs in free agency but know that none will come close to replacing Rob Gronkowski, the focal point of their 21-personnel passing game. It’s very possible that we’ll see New England utilize more 20 personnel (two backs, no tight ends) in 2019, with first-round pick N’Keal Harry playing the role of “tight end.”

Nobody knows what the Patriots offense will look like next year — at least from a personnel standpoint; the concepts will largely stay the same — but we can say one thing with 100% certainty: If the Patriots want a more efficient offense, they will cut down on those two-back runs in 2019.