Summer School 2021: Exploring 21 personnel

Summer School is back in session, and our overview of the most common offensive personnel packages now moves to the classic “21 personnel” package.

Last time we looked at the 11 personnel package, or three-receiver set. As we noted there, 11 personnel has largely taken over as the primary offensive personnel grouping in both the college and professional ranks. However there was a time — not that long ago — when a third wide receiver was seen as a gimmick, only to be used in emergencies such as long third downs or when trying to engineer late-game comebacks.

Before the 11 personnel package took over, teams tended to favor heavier personnel packages and the fullback was a common sight on NFL rosters. It says something about how most coaches in the NFL thought about the game of football that the 21 personnel package was referred to by many as the “Pro Personnel” set.

While two-back sets have largely fallen out of favor in the modern era, they can exist quite comfortably in today’s age of high-octane spread-influenced offenses. We could even see them begin to make a comeback around the NFL, though with much different execution than we were used to 15 or 20 years ago.

So what is the 21 personnel grouping, and how is it used in the modern NFL?

What it looks like

At its core, 21 personnel is two (2) backs, one (1) tight end, and a pair of wide receivers. This usually takes the form of a running back, a fullback, a tight end (usually in-line and attached to the end of the offensive line), and and a pair of receivers, lined up as an X receiver on the line of scrimmage and a flanker on the other side lining up off the line of scrimmage.

That’s the traditional “Pro” set, which usually sees the quarterback line up under center, with the fullback behind him and the running back behind the fullback in the I-formation.

The NFL typically uses this set as a running formation, particularly in short yardage or goal line situations. There are, of course, some more exotic and exciting options available to NFL teams. For instance, some teams will use a pair of running backs instead of a running back and a fullback. A pair of true running backs in the backfield gives the offense the ability to sow some doubt on the defense as to who has the football, as well as make creative use of screen passes or other receiving options out of the backfield.

The advent of the modern “H-back” (that is, a player who blends characteristics of a tight end and a fullback) also allows teams to force defenses to respect the possibility of a power rushing attack while giving them the option to throw the ball to a player who is likely a size or speed mismatch against a safety or linebacker.

Few modern NFL teams use the 21 personnel package as often or as well as the San Francisco 49ers under Kyle Shanahan. Fully 33 percent of San Francisco’s offensive snaps (344) have come out of the 21 personnel package, per Sharpfootballstats. Over the last three years, Shanahan’s 49ers have averaged 363 snaps (34 percent) of their total offensive snaps in a 21 personnel package. That is by far the most in the NFL, making them a strong case study for how the package can be used in the modern NFL. We’ll start by taking a look at a quick example of how the 49ers use the package to run the ball, followed by how they use it as a passing formation.

As a running formation

Giants fans, particularly ones who date back to the Tom Coughlin and Kevin Gilbride era, are likely already familiar with how 21 personnel and the fullback has traditionally been employed for much of the NFL’s history. For the most part, the team would line up in the Power I (diagrammed above), and use the fullback as a lead blocker to help knock a linebacker out of a running lane.

That is, essentially, what the 49ers do above, but they make some significant changes in how they present their 21 personnel package to the defense.

The 49ers’ alignment bares only a passing resemblance to a “traditional” 21 personnel package, instead they line up in the shotgun formation with the running back next to the right side of the quarterback. The fullback, Kyle Juszczyk (44) is lined up where teams normally put a tight end, next to the right tackle while their tight end, Ross Dwelly (82) is detached from the line on the right side and is partially hidden by the goal post.

Note: TE George Kittle was on the injured reserve this game

By concentrating their skill position players on one side of the offense, the 49ers are forcing the defense to shift defenders to the strong side of the offense in order to prevent a numbers advantage on that side of the field. After the snap we see both Juszczyk and Dwelly pull from the right side of the offensive formation, creating a numbers advantage for the offense on the play-side.

Using the tight end and fullback to create a numbers advantage where the offenses wants the play to flow highlights the appeal of the 21 personnel package. The use of alignment and play design by Shanahan highlights the versatility of the personnel package in the modern era.

As a passing set

While the 21 personnel package has traditionally been looked at as primarily as running set, some playcallers — Kyle Shanahan chief among them — have made good use of the set as passing package.

The fact that 21 personnel has historically been used as a running formation has, predictably, taught defenses to expect rushing plays out of those personnel packages. Therefore, they tend to play base (or heavier) personnel sets of their own, loading up on bigger defensive linemen and linebackers, and eschewing defensive backs. Those players also typically look to play downhill and fill gaps first when faced with an expected running play.

That is exactly what we see here from the Arizona Cardinals in response to San Francisco’s dense 21 personnel package. Arizona plays an eight-man box, with the cornerbacks tight to the defensive front, essentially putting 10 defenders around the tackle box. And while this would likely be an excellent run defense, it makes the Cardinals vulnerable to a passing play, which is what San Francisco has called.

It’s fitting that they set the touchdown off with play-action, as legendary 49ers coach Bill Walsh regarded play action (or “run-action”, as he called it), as the safest way for offenses to attack downfield. The play starts with San Francisco showing a pretty typical running formation with a tight “Power I” formation, with the quarterback under center, backed by the fullback and running back while the tight end and receivers are close to the bulk of the offensive formation.

The initial play-fake of the quarterback moving to hand the ball off to the running back while the offensive line, tight end, and fullback all move to run block is easily enough to force the Cardinals’ defense to honor their run fits. This gets the entire defense flowing in the direction of the supposed run play and the second level players all crashing downhill. However, we quickly see that Juszczyk is only faking a lead block and instead releases into a wheel route.

Because the defense is expecting a run play based on the personnel and formation, they are out of position and Juszczyk is able to out-flank them and score the touchdown.

This personnel package is useful for passes to each of the five eligible receivers, however defenses have something of a tendency to overlook the fullback in coverage, particularly when expecting a run play. This presents teams with an opportunity to find athletic fullbacks or H-backs and use them as weapons and not just run blockers or pass protectors.

Benefits of 21 personnel

Extra blockers

The primary benefit, and attraction, of the 21 personnel grouping is the availability of extra blockers. The offense gains a blocker who averages roughly 250 pounds by putting a fullback on the field instead of a third wide receiver. The potential benefits for running plays are fairly obvious, particularly in short-yardage and goal line situations when the run game is at its most valuable. In those situations the defense is naturally condensed and the game is at its fastest, and having an extra blocker to help contribute to a numbers advantage on the play side can be the difference between a touchdown and a fourth down field goal attempt.

The addition of a fullback, H-back, or even a second running back can also give the offense an extra pass protector for “max protect” schemes that keep a sixth, seventh, or even eighth blocker back particularly deep or slow-developing passing plays. These plays can be particularly effective when run out of well designed and executed play-action, which as we saw above, is something to which 21 personnel can lend itself.

Versatility

As with every other area of modern football, the ongoing arms race in both the professional and collegiate ranks has opened up new opportunities for a variety of positions, as well as new breeds of players to populate those positions.

In years past, the second back in a 21 personnel set was almost always a 260 pound fullback who was (essentially) a slightly smaller and more athletic offensive guard. His job was to be a battering ram for the running back and charge head-first into the defensive front, occasionally take a hand-off for a quick-hitting run to gain a single yard, and very occasionally catch a pass or two — Think Madison Hedgecock.

But as players get more athletic and teams look for any and every potential edge to advance the ball and score points, they have been increasingly looking at two-back sets. Not only are fullbacks getting more athletic and dangerous as skill position players (such as Juszczyk), shorter tight ends are being converted to “H-Backs”, adding athleticism and receiving skills to the backfield. Some teams, particularly college spread offenses in the Big 12, are even using two running backs and even omitting the tight end completely and playing 20-personnel packages.

As we saw with Kyle Shanahan’s 49ers, all of these options give the offense the ability to use schematic sleight of hand to show the defense one look, execute an unexpected play, and make good gains when defenders are out of position.

Passing game options

One of the interesting developments in recent years among more forward-thinking playcallers is the tendency to “go heavy to pass, light to run”.

As we saw with our look at the 11 personnel package, defenses react to offensive personnel packages and tailor their own sub-packages to counter the personnel an offense fields. We know now that defenses will use nickel or dime packages to counter 11-personnel sets, creating opportunities to run the ball efficiently. As it turns out, the opposite is true of 21 personnel packages, and defenses are much more likely to field “base” personnel packages to counter the heavier offensive personnel. That creates the opportunity for the offensive coordinator to scheme a match-up of a running back, tight end, H-back, or athletic fullback on a linebacker or safety. Those match-ups would likely favor the offense as those players are likely bigger than a defensive backs they would face and more athletic than the linebackers.

Drawbacks of 21 personnel

Less athletic

While fullbacks are getting more athletic and offensive coaches are finding opportunities to make use of players with unconventional size and athletic profiles as H-backs, the 21 personnel set still tends to be less athletic than other alternatives. And while that might not matter much to people with certain philosophies regarding the game of football, it does have an effect on the field.

Generally speaking, receivers run their routes further down the field than backfield players, which means plays involving receivers are going to be more valuable on average. By using a fullback or even a second running back as a receiver, the offense is exchanging a player who could be operating in the 10-15 yard area for a player who could be getting the ball in the 0-10 yard range.

This is somewhat mitigated by using an H-back or a running back who is an athletic and skilled receiver. That can help the offense keep a similar athletic advantage as 11 or 12 personnel packages (more on that one next week), but by and large the classic 21 personnel package doesn’t lend itself to high-octane offensive fireworks.

Lends itself to less creative play calling

The other main drawback of the 21 personnel package isn’t really a weakness of the personnel grouping itself, but rather how its thought of by coaches around football.

We’ve seen, clearly, that using two players in the backfield doesn’t hinder creativity and can actually help offensive coaches attack defenses in unexpected ways. However, there can be a tendency for some coaches to fall back on received wisdom and the 21 personnel package can act as a security blanket. We know that lighter personnel packages can actually make running the ball easier, however some coaches can be prone to going heavier for more bigger bodies to try to move the ball through sheer bloodymindedness.

The saying “when all you have is a hammer, every problem is a nail” can certainly apply when it comes to talking about the 21 personnel package. There are certainly times when using bigger bodies can help when brute force is the best way forward, but there can be tendency to fall back on it when it isn’t necessary. If teams start running into the strength of a defense when they don’t have to, it can hold them back and lead to forced passes in third-and-long situations.

Of course, the tendency for some coaches to revert to that mentality when fielding heavy personnel sets could be a big part of the reason why the 21 personnel package can be so useful for creative play callers.