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A closer look at the Celtics 21 series

The Celtics had a reliable system out of their 21 series, and went to it early and often throughout the season.

2022 NBA Finals - Golden State Warriors v Boston Celtics Photo by Noah Graham/NBAE via Getty Images

Early offense reigns supreme in the NBA. If you can generate solid scoring opportunities before your opponent has a chance to fully set their defense, you’re operating from a position of strength, and generally speaking, begin to set the pace of the game.

Coaches have multiple sets and series that they like to deploy when looking to generate early offense, with one of the most common series being ‘21’ — a guard-to-guard action that occurs on the wings during a five-out offensive alignment.

For description purposes, the series is known as ‘21’ because it involves the point guard (the 1) and the shooting guard (the 2). If your team generally operates with a point forward - a la Jayson Tatum, then you will see the series run with the forward in place of the point guard.

Every team has its own take on this series, and deploys it in different ways, as they continue to look for ways to catch the defense off guard and force favorable matchups. Ime Udoka is no different, and throughout this past season, we saw the Boston Celtics initiate their offense through multiple different 21 sets.

As we look ahead to the new season, I found looking back at some of the Celtics' more utilized versions of their 21 series to be a fun exercise, as it could give us a solid foundation in knowing what to expect from them moving forward.

21 Chase

This is arguably the most common version of 21 across the entire NBA. 21 Chase is a set that sees a ball-handling guard and off-ball guard exchange the rock around the wing, with the guard tandem operating in a little give-and-go action.

As you can see, the play starts with the ball handler (Dennis Schroder) kicking the rock to the shooting guard, Schroder then cuts towards the ball hand and receives a hand-off, forcing the defense to switch and chase the action, while Schroder turns the jets on to generate an easy lay-up.

21 Chase can be initiated either at the elbow or around the wing/slot area of the court.

One thing Boston did to keep defenses guessing, was put Tatum as the second man in the action (the one initiating the hand-off) in a form of ‘Elbow Get’ action. Yet, as Tatum is often utilized as the ball handler, and the action still involved the point guard, it would still fall under the 21 Chase umbrella — although Tatum did execute this set with wings too, but that’s another story.

By adding Tatum into the action, you’re increasing the scoring gravity involved within the set, which forces the defense to alter their pick-up point, so, when the hand-off occurs, it’s easy to blow the defense open and generate an open lane to the rim. Furthermore, you’re forcing the weakside low man to commit to defending the rim, so the corner kick-out is often available if required.

21 Nash

This is probably my favorite 21 set, because of the pressure it puts on the defense, and how quickly the set can generate multiple mismatches across the court.

21 Nash is a simple concept. With all the screening actions involved, it can quickly devolve into a nightmare for a defense. The concept is simple:

  • Point guard pushes the pace and passes to the shooting guard on the wing
  • The point guard and a center then flow into a stagger screen for the pass receiver
  • Pass receiver then curls over the stagger screens and attacks the defense — usually by driving middle

In the above clip, you will see that Jaylen Brown is the recipient of the pass and stagger screen. Unfortunately, Brown hesitates atop the perimeter, which allowed the defense time to recover. Sure, Payton Pritchard eventually scores, but the point of this play is to attack quickly and punish the gaps while the defense adjusts.

Below is another 21 Nash set, but this time with Tatum operating as the initial pass receiver.

21 Reset

Whenever you implement a system, you need to account for the defense reading it and shutting it down. Enter ‘21 Reset’, an option of the series which allows you to reset the offense before looking for new ways to break down you opponent.

If you initiate the guard-to-guard action and the defense stands firm, swing the rock to the big man at the top of the perimeter, allowing the offense to reset before looking for its next offensive option.

The above clip is a solid example, as you can see Marcus Smart enter the 21 action with Jaylen Brown, the Sacramento Kings read the set well, and the defense stands strong. Brown kicks the rock back to Al Horford to reset the offense.

Here’s where things get interesting. Boston initiates a split cut between Smart and Brown, allowing Horford to fire an entry pass into the cutting Brown for an easy finish around the rim.

Of course, the split cut is an action upon itself, yet it does drive home how useful resetting a play can be, especially when attacking in early offense and looking to maintain an advantage.

21 Keep

The naming of this set makes things easy to envision - the player that receives the pass keeps the ball. Again, this set is usually reserved for guard-to-guard actions, but Udoka consistently placed Tatum into the set to add confusion and get the Celtics best scorer some easy looks in the early part of the shot clock.

Here’s a possession against the Golden State Warriors in which Smart pushes the pace, hits Tatum with the pass, and the St. Louis native spins off his man to attack the rim.

You can see Tatum pauses after receiving the pass, to keep the defense guessing, and offering 21 Chase as a decoy set.

Another part of ‘21 Keep’ that needs to be remembered, is that the big is usually hovering near the action, so that they can set a screen if the pass receiver chooses to come over the pass/hand-off, which is why you can see Williams slow down his run and slightly start to edge over towards the possession before Tatum opts to spin off his man.

Here’s a more traditional look out of the 21 keep series:

You have the pass/hand-off between Smart and Brown, and then the screen from Williams. You would ideally want the screen set much sooner, but that’s what makes the Golden State Warriors so good! They’re incredibly disruptive on the defensive end.

Final Thoughts

Running any form of offensive set is always a good option if you’re looking to get your team a quick bucket and develop some offensive rhythm. But, there is always a time and place for coach intervention — which is why a system such as 21 is so useful, as it’s primarily based on what the defense is showing, and allows players the autonomy to simply flow into the action(s) at will.

Of course, there will be principles in place, such as when to keep, when to chase, and most importantly, when to reset. Boston has added another high-IQ guard to their rotation this season, and it will be interesting to see how their 21 series evolves to incorporate Malcolm Brogdon, either as the initiator or pass receiver.

However, the most exciting part is simply to see the variations Udoka puts in place and how he utilizes the plethora of multi-skill talent he now has on his hands.

One thing’s for sure — it’s going to be one hell of a season!