Monday, July 2, 2012

Mens_Rea Teaches You Things About Basketball pt. 2 - Defense and Its Consequences


Last time we took a detailed look at the type of movement offensive players make on the court to increase their chances at scoring. This time, we're going to look at the other side of the court - defense. Just as we described the offense's main goal as scoring points, we can just as simply characterize defense's main goal as preventing the other side from scoring points.

We'll start by looking at the different types of defensive schemes, then we'll see how screens affect how the offense and defense interact with each other, and we'll finish by comparing our systems.

Defensive Schemes

Defense can be categorized under three major types: man-to-man, zone, and hybrid man-zone. We'll begin by identifying these three types and then we'll compare them.


Probably the most straight forward defensive schemes is man-to-man defense. The defensive scheme operates as the name suggests - each defensive player matches up with a single offensive player and defends him.

Let's look at an animation to demonstrate.

In this animation the SF is setting a screen for the SG and the SG's defender attempts to stay with him.

Man-to-man defense is ideal if your team's roster has excellent individual defenders that are able to stay close to their man. However, as we saw in part 1 and we'll continue to explore, offensive systems are well suited to take advantage of man-to-man defense by setting screens to free up offensive players. For this reason, teams rarely play strict man-to-man defense.

Zone Defense

Generally, zone defense prefers to assign areas of the court to individual defenders rather than a specific player.

For example, here we see the zone of responsibility for each defender in a 2-3 zone.

Similarly, zone defense can be organized in a 3-2 set, a 1-2-2 set, a 2-1-2 set, and practically any other set you can imagine. In the NBA, zone defense must be slightly modified in certain sets to prevent a 3 second lane violation call. This is achieved by stepping out of the lane constantly or picking up players that run though the lane (remember that a 3 second call timer resets when the defender in the lane is actively guarding an offensive player - in practice reaching out toward an offensive player within arm's reach is sufficient).

Each type of zone defense has built-in weaknesses in coverage. In the example of a 2-3 zone, we see some areas of weak coverage in the corners, baseline, top of the arc, and around the freethrow line (not pictured well here). Any area where coverage by a single player is stretched further from the center or coverage overlaps and it's unclear which player has responsibility is a potential area of weakness. Also, zone coverage generally stresses interior defense over perimeter defense and is much more willing to allow the offense to freely pass  or shoot along the perimeter.

Let's see an example of how zone defense reacts to ball movement.

Notice how the defense attempts to discourage driving lanes by constricting toward the ball and tries to maximize help defense. Also, notice that the zone can trap the ballhandler in some situations by cutting off passing options or forcing dangerous passes.

Zone defense is a good option if your team is well coordinated, is not athletic enough to prevent dribble penetration through individual defense, and is willing to allow perimeter jump shots from the opposing team.

Hybrid Man-Zone

There are two types of defensive schemes that are neither fully man-to-man nor fully zone defense. The first is called Modern Swarm Defense. Modern Swarm Defense is the most commonly used defensive system in the NBA and in the balance between man-to-man and zone defense, it weighs more heavily toward man-to-man.

Modern Swarm Defense begins as man-to-man defense but the team will strategically switch defensive responsibility off of screens or try to create double teams.

The animation above illustrates a strategic double team on the Center to take away a perceived advantage that he has. The defense rotates to force the player furthest from the ball open and attempting to force a dangerous pass. If the Center is able to locate the open SF, due to the distance of the pass, the defense has more time to react appropriately. Let's look at a longer animation and a video clip to demonstrate how this works.

Here, the defense strategically tries to force the ball out of Dirk Nowitzki's hands on the elbow. The defense continues to rotate after the pass and contest the shot by another offensive threat, Jason Terry. Notice how proactive Modern Swarm Defense is. Rather than read the offense and contest apparent shot opportunities, Modern Swarm Defense tries to force the offense away from its options altogether and force difficult decisions by the offense.

The other type of hybrid defensive scheme is called a match-up zone. This system weighs the balance between man-to-man and zone more heavily toward zone. A match-up zone will attempt to force a specific individual match-up similar to man-to-man but will do so within a zone defense.

In our match-up zone animation the defense is operating in a 2-1-2 zone but is also attempting to force a match-up at the SF position by switching defensive responsibilities within that zone.

Both systems of hybrid defense can be criticized as high risk/high reward systems. Hybrid systems have all the benefits of man-to-man and zone defense but also have all the risks of both systems. Execution is the balancing factor between the benefits and risks - good execution is able to minimize the risks while maximizing the rewards.

Reading the Screen

Before we compare the different defensive schemes available, it's helpful to understand the options that come out of screening. As we discussed in part 1, there are a variety of different screens but no matter the type of screen, the goal remains the same - free up the offensive options. Let's look at how both the offense and defense react to screens and from this we can more easily compare our schemes. It is very important to remember, especially when we move to analyzing plays, that good players do not run off of screens - they read them. What I mean by that is offensive players do not simply run through a designed play as if they were following a pattern, they will move based on how the defense is playing them.

For simplicity's sake we're going to start with the SF setting a screen for the SG and the SG's defender attempting to contest. We'll go step by step through the animation to show where our different options open up.

So far the SG is running toward the set screen with his defender trailing closely behind him. It's at this point that several decisions have to be made. The SG will have to make a judgment as to how he believes his defender will react to the screen. If his defender is close behind him and believes his defender will follow him around the screen, the SG has a couple of different options.
The SG may take a flare cut to distance himself while his defender is caught on the screen. This option is generally more effective for players that are adept perimeter shooters or if for some reason the lane is covered.
Another option is to curl tightly around the screen, effectively sealing the defender behind him.

What happens if the defender decides to cheat the screen, or move to where he believes the SG will go?
Our flare is now much less effective because the defender is able to deny the passing angle and is taking a shorter path to the desired location. However, there are counters to cheating the screen.
One counter is to cut back under the screen to receive the pass.
Another is to flare wide and in the opposite direction.

Now we'll add our SF defender and see how some team defense can add to the complexity of playing the screens.
This time instead of the defending SG attempting to stay on his man, the SF defender switches on the screen to help cover the SG. By switching off of the screener, the pressure to cover the SG is alleviated significantly because the switching defender can cover certain angles by simply hedging one way or the other (e.g. staying high off his man to quickly gain position on high flares). Notice that it could also potentially create a mismatch since the SF is now covered by the opposing SG and the SG is now covered by the opposing SF. 

This is a reoccurring theme in basketball that you should try to constantly be aware of - when you take something you should be prepared to give something. Here, we're taking away the advantage of the offense's screen but we're giving them a potential mismatch.

Let's add some motion to our SF and see how the dynamic changes.
As we just identified, if the defense switches off the screen, the SF can immediately seal the opposing SG and try to exploit that mismatch.
If the defense pays too much attention to the movement of the SG, the screener can quickly cut to the basket for an easy shot.

As we move forward, remember that these options exist and that screens are opportunities to force the defense into a difficult decision. A well-executed play is not merely running a pattern but rather it is correctly reading the defense and selecting the best options that open up.


Now that we're more familiar with the different defensive schemes and the role screens play, we can make a more informed distinction between the different schemes. Notice how the role of screens is designed almost exclusively to beat man-to-man based defensive schemes (either straight man-to-man, swarm defense, or to a lesser extent match-up zone). For that reason, it should be apparent that it would do our offense very little good other than to free up a pass to an area of weak coverage to set screens if the defense is playing zone.

For example, compare a play similar to what we just examined under man-to-man and zone defense.

2-3 Zone
Notice that in our zone coverage, the defense was free to ignore the screen set by the SF because the zone isn't concerned about staying on him. However, remember that one of the weaknesses of zone defense is perimeter shooting and thus it might have difficulty contesting on this particular shot.

Closing Thoughts

Obviously there is much more to defense than I covered but hopefully this gives us a starting point in discussing how defense sets itself up and interacts with the offense. Eventually, we'll move along we'll take a more in-depth look at specific defensive situations but we now have the foundation we need to examine full plays. In part 3 we're going to start with some very basic plays that are found across different offensive systems and then we'll look at a few popular offensive systems.

If you're wondering about the different cuts from part 1 at the bottom, the ones I spotted were a UCLA cut by the PG followed by a back cut by the SF, a curl by the SG, then a cross cut by the C, a banana cut by the PG, and a flex cut by the SG. If you saw something different let me know, it's very possible I missed something.

Before we end here let me give you a hypothetical situation to think about.

Suppose you're a defensive coordinator for an NBA team and after some scouting you determine that the key to the opposing team's offense is defending a low screen set for the SG by the SF similar to what we examined above with effective isolation of the PG, SG, and SF. Similar to this diagram:

The SG is quick, reads screens well and can convert in the lane or out along the perimeter. The SF on the other hand is fairly slow, has bad hands, and is very poor at low post scoring. Your SF is of average speed but definitely slower than the opposing SG and your SG is similarly of average speed and slower than the opposing SG.

What defensive scheme would you rely on to defend against this scenario? How would you instruct your players to react to the screen set by the SF? Can you identify how you have allowed the offense to attack you?

Next time I'll give you my thoughts on this scenario and we can see how they compare to your own.


  1. Thanks for another great post, Mens Rea.

    I'm going to take a crack at your closing question.

    First off, their 2-guard doesn't sound like someone either our 2-guard or 3-man can check by themselves. So going man-to-man isn't going to work.

    And given his shooting process, pure zone is a bad idea too.

    The best way to proceed would be by employing a swarm defense, for three reasons:

    1.) It allows us to double their 2-guard when he catches the ball, which is ideal because we don't have anyone who can guard him capably man-to-man.

    2.) It forces them away from their game plan and prevents them from being able to exploit that matchup with the screen.

    3.) Their best way to counter and beat us would be by making quick passes. There's no indication that they're particularly proficient at passing.

    Thanks again!

    1. Hi James,

      I'm glad you liked the post. I don't want to comment too much on your response in order to give others an opportunity to give the scenario some thought but I would say that's a good approach.

  2. Thanks!

    I'm looking forward to more of your stuff in the future.

    Are you writing anywhere besides here and Reddit?

    1. Nope, just here and there.

    2. Cool! Let me know if there's ever anything I can do to help.

      I'm a scout and I do web design, too.

      James Kerti


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