Before I got a job in the NBA, I badly wanted to learn more about NBA Xs and Os, but I didn’t know how. I bought books and read all the articles I could, but I couldn’t find one place to teach me the terminology and the strategy of the game that I loved. That was many years ago, and while blogs and social media have made it so that there are now a host of people talking about Xs and Os, there still aren’t many people truly teaching them—especially not in a way that is accessible to those without technical basketball knowledge in the first place.

Eventually, I did learn Xs and Os. You know what it took? Working in professional basketball for almost a decade. I learned by breaking down thousands of hours of film, sitting in NBA coaches meetings, and participating in the film sessions given to players. But I’ve always believed there should be an easier way.

Which is why I’ve teamed up with the great Gibson Pyper of Half Court Hoops and The Basketball Playbook to make an in-depth course on NBA Xs and Os.

This article is an adaptation of one of the 40+ lessons in the course. If you’re thinking of purchasing it, my hope is that it gives you a taste of what the course is like. And even if not, I hope this article is a useful resource to help you understand NBA defense better.

Here’s a simple framework to think about halfcourt basketball: the offense works to create an advantage, and then aims to capitalize on that advantage. That means the defense does the opposite: they work to not even allow an advantage in the first place, and then if they fail at that, they work to neutralize any advantage that was gained.

Think about a ball handler going against a defender. The first goal of the offensive player is to gain an advantage: to try to create an opening to take a shot, or get a step past the defender on a drive. The defender’s goal is to not allow any advantage. When people talk about defense in basketball, this is what they typically think of: guarding the ball and stopping any advantage from being created in the first place.

Help

But let’s say the offensive player manages to get past their defender. In that case, the defense has to react to that advantage and try to neutralize it. That’s where help comes in. The defender’s teammates need to move to try to stop the advantage, otherwise they will allow a layup. So a teammate will slide over to get in front of the driver, providing help.

When that happens, the offensive player might force up a shot, or try to drive through both players, but their odds of success are much lower than before the help arrived. The defense, by helping, has mostly neutralized the advantage. But not completely, because that help has opened up a teammate. So if the offensive player passes to his now open teammate, then the advantage is maintained. The defense has to rotate again in help or the offense will get an open shot. They have to help the helper.

Recover

Let’s say our driver sees the help and passes to his open teammate behind the three point line. Perhaps the helper anticipated the pass, reacts immediately, and sprints to get back in front of the receiver before they can get off a shot.

That recovery is a kind of closeout. Any time a defender is trying to close the distance to a perimeter player with the ball we say they are closing out on the player. Close outs are often difficult to execute well, since the defender is in recovery mode. They have to get out and contest the shot (i.e. get a hand up to try to bother the shot), or at least scramble to get into a good guarding position. Because they are rushing out at a player, they are more vulnerable to pump fakes or the player driving past them.

Against shooters, defenders will close out faster and closer to the shooter’s body, since they are more concerned about the shooter getting any kind of shot off. This is called a hard closeout or a long closeout. When a defender closes out hard on a shooter, their main goal is not to allow any clean shot, and will live with it if the player drives past them:

Sometimes this even means ending up with a fly by contest, where the defender goes right by the shooter in an effort to run them off the line (i.e. get them to drive inside the three point line). When defenses realized the value of three point shots and fly by contests became more popular, shooters figured out a counter: pump fake and take a dribble to stay in place or step to the side and still get a three pointer off.

On the other hand, if the player isn’t a shooter, defenders will want to close out short. They will aim to stop much further from the offensive player, so that they prioritize regaining their balance and staying in front of any drive, since they know the player is not a threat to shoot:

A well executed closeout can take away the offense’s advantage. When that happens and the defense has recovered (gotten back to their ideal spots), the offense will have to work to create another advantage.

This is, ultimately, the goal of good help defense (particularly given the NBA’s relatively short shot clock). Defenses can never stop all offensive attempts to gain advantage: even a simple, well set screen creates a momentary advantage for the offense. But great defenses can often neutralize those advantages through well-executed help.

Help Principles

That’s why good defense is a team effort. Without teammates helping, the offense will score much more easily.

But getting players to help is only step one for a coach. The second step is figuring out the rules that govern their help: where is the help supposed to come from? Should teams help out of the corners, and how much? Who is the first line of defense in help? How far should players help off of the three point line? Without these rules, multiple players might think they’re the first line of defense, collapse on drivers and leave teammates wide open.

Different coaches have different philosophies on these help rules, of course. High school coaches and college coaches approach these subjects far differently from NBA coaches.

In recent years, the NBA has converged on certain help principles that are largely similar across teams. These rules are fluid as the game continues to evolve, and there are some signs that forward thinking teams are revisiting these principles. But at this point in time, there is a fair amount of overlap in philosophy on three main, related points:

(1) Help should come from the weak side
(2) Do not help out of the strong side corner
(3) The first line of defense at the rim comes from the low man

Help from the weak side

Remember why coaches want defenders to shift toward the ball more the further their matchup is away from the ball? [Editor’s note: this was explained in an earlier lesson.] Because the further their matchup is, the less of a threat they are to get the ball quickly. A pass to them means a long pass, often looped overhead, giving defenders time to recover.

The same reason dictates why coaches want help to come from the weak side. If the help comes from the strong side of the floor, it’s an easy pass to a wide open player. If it comes from the weak side, it’s a difficult pass that takes time to arrive.

Don’t help from the strong side corner

A particularly important part of this philosophy at the NBA level is not helping out of the strong side corner. At lower levels, where shooting is at a premium and corner threes aren’t any different than non-corner threes, coaches may encourage help from the strong side corner: it can cut off a drive before the drive gets the rim, and the player who’s left open doesn’t have as much room to navigate once catching the pass because they’re hemmed in by the baseline and sideline.

But in the NBA, the opposite is the case. Corner threes are very high value shots since they are closer to the basket, and the NBA is full of great shooters who would feast on open corner attempts.

So NBA coaches are loathe to have their players fully provide help from the strong side corner. Some teams will ask their strong side corner defenders to step in and jab in at the ball, but most will not want them to fully help and stop the ball. Even if an offensive player has an open drive to the rim, many coaches will want the defender not to leave the corner shooter and instead to trust that help will come from the weak side.

The first line of defense is the low man

So who is expected to provide that help at the rim? It’s the weak side defender lowest on the floor, closest to the basket, what is termed the low man.

This is a simple rule that helps capture much of what we’ve just covered. It makes sure that the help at the rim comes from the weak side defender who is best in position to help at the basket. By creating a simple rule like this, it allows defenders to have clarity on who has the help responsibility. That clarity is key, because when a situation arises where help is necessary, there isn’t time to think. Players have to just react.

Rotations

At the lowest levels of basketball, that first line of help might be enough to neutralize the advantage. But at the NBA level, offensive players are so good that they anticipate the help and will make the right pass when that help opens up a teammate. So the better the offense, the more defenses have to focus not just on the initial help, but on how to cover for their helping teammates, to help the helper. This second line of defense is not just about the help, but about the rotations in behind the help.

Perimeter Rotations

The most straightforward kind of rotation on the perimeter is a full rotation. A full rotation is a chain reaction: if an offensive player on the perimeter catches a pass, the player nearest to them will rotate over and help. The player who is now open will be taken by the next closest player. And on and on, like this:

In this case the player who initially helped does not aim to recover to their initial matchup. Instead they recover to the end of the rotation chain, and the matchups are now switched.

A full rotation involves a lot of movement and scrambling, and therefore good offenses can find open shooters with good ball movement. That’s why the use of full rotations has declined a lot in the NBA in recent years. But when executed with the proper effort and precision it can make it very hard for offenses to get open looks.

Instead, about a decade ago, the NBA started trending toward a help and recover model. In this method of help, the player who helps is responsible to recover to their matchup and contest the shot as best they can.

They get support from the next player in the help chain not with a rotation but with a stunt. That player fakes as if they’re going to help, trying to freeze the pass receiver and buy time for the receiver’s defender to recover to them. After the stunt, they recover to their own matchup. You’ll often see this as a stunt into the passing lane to make the quick pass even more difficult.

When executed properly, then, the stunt and recover doesn’t fully open up any shooters, particularly if the offense doesn’t have good spacing. NBA teams, though, have figured out how to design sets that position their players such that the distance it requires to stunt means that defenders can’t stunt effectively without leaving their matchup open. With so much shooting and spacing on the court, stunts in rotation are not as common. Teams instead will either rotate more aggressively, or not rotate at all, based on the matchup.

In the case of no rotation, the defense is just willing to leave that player open on the perimeter:

Rotations are reflexive and happen very quickly, so players need to be acting off of instinct as much as anything. But coaches will still try to choose their style of rotation based on who catches the ball on the perimeter.

“KYP,” a coach will say. “Know your personnel.” Great defenses don’t just blindly follow rules, but tweak their rules depending on who has the ball. Coaches may highlight a few major threats that they want to fully rotate to, and a few non-threats they want to avoid rotating to, and trust their players can follow the scouting report in the heat of the moment.

Interior Rotations

The most important situation for the defense to help the helper happens when help comes from a defender near the rim. In that case, the offensive player they’re guarding is perfectly positioned for a layup, dunk, or offensive rebound. That means if the defense doesn’t help the helper and rotate to defend the newly open player, the offense is likely to get a very high percentage shot.

This kind of helping the helper is called a sink, where a perimeter player sinks down to take away the interior pass, like this:

The nearest other helper then has to cover for the player executing the sink by filling, aiming to position themselves so that they can rotate to whoever gets the ball:

After executing this sink and fill, there are two main ways for the defense to recover on a pass out. They can simply recover back to their original matchups, like this:

Or they can x-out, where they exchange matchups, recovering in an “X” shaped pattern:

An x-out is a method that allows the defense to recover based on who is closest to the player receiving the kickout pass. If the fill player is closer to the receiver, they will rotate and trust their teammate to take their original matchup. In that way it’s somewhat like a full rotation: it scrambles the matchups, but is more likely to cover open players.

Screen Defense

One note here before moving on: Defending a screen is a kind of help, but a very specific kind. To make that clear, I don’t call someone defending a screen a helper. Instead they are a screener defender, because screener defenders have very specific responsibilities dictated by their team’s chosen coverage (as we’ll see soon). Help, in this way of thinking, is more of a reaction than it is a pre-practiced response to a screen. So it’s important to try to separate out screen defense from help.

Zone

So far this has all been about man to man defense. These rules are quite different for zone defenses. In a zone, the help defense principles are based on what type of zone is played: a certain flavor of 2-3 zone has one set of principles, while a 1-3-1 or a 1-2-2 would have different ones. There are too many of these rules to cover, then, and since our focus is more on the NBA, where zone is far less prevalent than at other levels, we won’t go into great detail here.

But it’s important to note that one big difference in zone help principles is that while in a man defense the help rules change based on where the player is on the floor, in a zone, the position the player plays is most of what dictates the rules. If you’re playing the top of a 1-2-2 you’ll have different help rules than playing one of the bottom forward positions. And since that position doesn’t change over the course of a possession the way help responsibilities do in man defense, it can make things simpler.

If you found this lesson interesting, check out the full course!