How NBA defense has changed over time

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Let’s start at the top. The goal of modern NBA defenses is the same as it’s always been: prevent the other team from getting buckets. Simple, right? The easiest and most efficient place to score is at the rim; both offense and defense are designed from the bottom up to create or prevent layups and dunks. (Important context: although the midrange has declined as the three-pointer has become more prominent, the share of shots at the rim has barely budged over decades. Offenses have mostly just exchanged medium-length jumpers for long-distance jumpers!)

In the olden days, offensive limitations meant that the post-up was the easiest way to get shots closer to the basket. Ballhandlers had far less flexibility to do things taken for granted today, like taking a gather step, or, uh, changing direction; snot-nosed kids laugh at clips of NBA players from the ‘60s and ‘70s dribbling, but your average point guard from today would be called for carrying before he crossed half-court back then.

With far less ballhandling leeway and less emphasis on long-distance jump-shooting, it was difficult for smaller players to navigate a more crowded paint to get to the rack. It was easier to pass it into a posting behemoth. Sometimes, that could result in nifty footwork and pretty dunks; other times, it might mean a twelve-foot fadeaway.

The physicality differed, too. Most NBA fans know that the hand-check was a popular perimeter defensive maneuver that was slowly but surely litigated out of the game before finally being banned outright in the early 2000s. What’s not as easily understood unless you’ve watched a lot of old game footage is how quick whistles were on the inside compared to today, too. Sure, the lowlight fouls people remember were far harder than what you see in non-flagrant situations today, but refs would whistle even slight contact in the paint that would never get called now. Dumping it in the post wasn’t just the easiest way to get close to the basket; it was the easiest way to get free throws.

For what it’s worth, the hand-check stuff was always slightly overblown. Despite its technical illegality, you still see it today, albeit less aggressively, and there are other rule changes (either by the letter of the law or through enforcement) that have been greater enablers of the offensive explosion we have seen in recent years.

1996 – USA TODAY Sports

But enough about offense. On the other end of the court, the most important change was the elimination of illegal defense rules in the 2001-02 season, although it took years for the ramifications to be fully understood and exploited.

Previous illegal defense rules meant that teams were relatively helpless in their help principles. In the ‘70s, there was a three-foot rule: players had to stay within three feet of their defensive mark at all times. That, predictably, led to a lot of clear-outs and isolations.

In 1981, the league instituted different and more confusing illegal defense rules. The short version: big men defenders had a little more leeway on positioning, but perimeter players guarding opponents up top still had to be near their man. They were not allowed to duck below the free-throw line or cross from the weakside to the strongside if their mark stayed still.

Think about how remarkably limiting that would be by today’s standards! The dissolution of those rules in 2002 would eventually be the biggest change agent in modern defensive strategy, allowing players to guard space and move more or less however they wanted (as long as they kept moving; the league also instituted the defensive three-second rule to mitigate the obvious strategy of having a human tree camp out at the rim swatting everything in sight).

That meant that up until the early 2000s, there was only so much coaches and players could do. Switching occurred, but usually as a last resort, since teams didn’t like giving up a size advantage when it was harder to provide help defense. Mouse in the house, barbeque chicken, etc.

Put another way, defense in the before times was more reactive. One-on-one defense was key. If you couldn’t stop your man, the team’s options were limited, and your squad would likely have to send a hard double. The pick-and-roll, which requires more team coordination, certainly was a standard play, but it wasn’t happening every time down the court like it is today (unless you were on the Jerry Sloan-era Utah Jazz teams or a few progressive peers).

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However, things have changed. Individual ability still matters, of course, but off-ball and help defense have become more critical components of a strong team defense. Offenses are elite at manufacturing the perimeter matchups they want, so teamwide awareness has never been more important. In response, defensive positioning has become far more proactive, ready to help on the inevitable perimeter mismatch.

Full-on zone defense, as a rule, is still remarkably rare. This year has seen more zone defense than ever before, and still, only three teams run it more than 8 percent of the time (per Synergy). It’s consigned chiefly to after-time-out situations or if teams are desperate for a curveball for a few possessions.

But zone principles are now involved in every single action that takes place on the floor.

Nail help (and its kissing cousin, nexting), something largely forbidden before the league eliminated illegal defense rules, is a good example. In today’s game, most defenses will attempt to crowd the dribble-drive by placing an off-ball wing near the free-throw line, ready to harass drivers and sprint out to the nearest three-point shooter. That used to be disallowed!

Switching has grown in prevalence, too, for a few reasons. First, switching helps flatten out the pick-and-roll attack by crowding ballhandlers at the level of the pick, limiting their room for a pull-up triple. In the old days, a switch would invariably result in a pass to the big man rolling down the paint with a helpless little trying their best to stymie him. Now, however, smaller players can A) get away with more physicality, allowing them to fight harder for positioning, and B) front a big with the confidence that teammates are ready to help behind them. It used to be hard for defenders to be in a proper help position if fronting failed; now, it’s a basic expectation.

(Anecdotally, switching doesn’t seem quite as popular now as it was five or so years ago; offenses learned to take advantage of switch pockets by slipping screens to create a 4-on-3 situation as the roller accepted a pass while moving toward the hoop. But it’s still a common tactic that gains even more importance in the playoffs.)

Other help principles evolved, too. The idea of the “low man help,” which usually means shrinking the weakside corner defender into the paint as a deterrent at the rim, became more common. Think of it as a one-man zone. Entire chess matches in playoff series develop around offenses and defenses trying to manipulate weak or strong defenders into low man help positions. Watch Derrick White (the league’s best non-big low man helper) ignore a depressed Jonathan Mogbo in the corner to lurk in the under the basket, ready to swat Gradey Dick’s layup away:

Now watch when it’s Trae Young in low man help (although Jalen Johnson deserves plenty of blame, too):

See the difference?

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Tagging the roller, another move less commonly seen in the illegal defense era, is now a staple of every pick-and-roll defense. At its core, tagging is simply helping the helper. When a player sets a screen and rolls, most defenses require a third defender to “tag” the roller to disrupt his timing and (usually) allow the defending big to recover back to his mark. Sometimes, it’s a simple dart into the roller’s way before dipping back to the perimeter. Sometimes, it’s a full-on forearm shiver. Usually, it’s something in between, like Andrew Nembhard briefly stonewalling Onyeka Okongwu here (although it doesn’t matter thanks to a gorgeous dime from Young):

We mentioned that the zone is uncommon, but certain teams (Miami, in particular) have run it well. (I go deeper on zone defense usage here.) Zone defense tends to see most of its work when a set play is coming, such as after a timeout, but teams are increasingly willing to use it for a few live-ball possessions in a row to disrupt any rhythm an offense is in. It doesn’t always resemble the 2-3 your high school coach taught you, however. Former Pistons and Raptors coach Dwane Casey once noted that “the way teams have bastardized the zone so much and tinkered with the zone, it’s really a glorified switch.” That’s a concise way to think about it.

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One of the most striking aspects of current NBA defenses is their increased complexity compared to those of the past. I want to re-emphasize that this isn’t a knock on old defenders or coaches; rules have changed in a way that allows far more creativity nowadays. But in a single given game, you’ll see teams run five or six different coverages to stop a pick-and-roll. Players are expected to have perfect communication and flawless recognition; any team’s minimum-salary end-of-bench veteran can and will drain a three in your face after the slightest misstep. The margin for error is so small.

Defenders today often look and move differently. The muscle-bound bodybuilders of the past are mostly gone, replaced by leaner, more leopardine players. Both offensive and defensive players have to move far more than in previous eras; tracking data has proven that today’s players cover more mileage in a game than ever before. There’s more off-ball movement, too, so all five defenders need to be on a string.

Versatility is key. Centers often guard jitterbug point guards on the perimeter, and the rise in three-point shooting and offensive spacing means defenders must be nimbler and quicker to react. Few bigs have the luxury of waiting in the paint and rising up for a contest as someone backs down and tries a jump-hook over them; now, they have to 2.9 in and out of the paint, close out on a shooting threat in the corner, and then sprint back to the rim to help deter a drive. It’s a lot of work!

Even close-outs today can differ significantly from those of the past. The days of the choppy-stepped close-out to crowd shooters without going airborne are increasingly scarce, and the “Zaza rule” has curtailed the most reckless straight-on close-outs. Close-out strategy will change on a team-by-team and even player-by-player basis, but many defenders are taught to fly to the side of dangerous shooters to disrupt both the three-pointer and the next pass. Watch as Tyrese Haliburton subtly changes his close-out angle mid-stride to prevent a pass to the side and avoid fouling (although it doesn’t stop the shot attempt in this example):

On the flip side, teams are increasingly willing to not close out on non-shooters at all, particularly in the postseason. Just the other night, we watched the Grizzlies completely ignore famed backpack-wearer Draymond Green. Clank:

This trend follows directly from the help principles we’ve discussed above and gives rise to an increasingly common defensive strategy rarely seen in the pre-2010s: stashing a rim protector on a shaky perimeter player. Steve Kerr famously employed this tactic to allow mountain man Andrew Bogut to roam off 6’4” non-shooting defensive ace Tony Allen, forcing Allen off the floor in a critical playoff series.

The league took notice. Coaches all over the Association are now willing to put their best rim protector on an offense’s worst shooter, daring weak links to do something with the acres of space given to them while keeping the big close to the rim to contest layups.

Two more common strategies you might hear about are peel switching and scram switching. The former is conceptually simple and has been around since the early days of basketball: if the on-ball defender gets beat off the dribble or on a close-out, a help defender will slide over to the ball, and the beaten defender will retreat to guard the helper’s man. Watch Santiago Aldama here as he gets beaten by Buddy Hield and peel switches onto Jimmy Butler:

Scram switching is a variation of pre-switching in which a weaker defender is swapped with a stronger one before a post mismatch can occur. Usually, it’s to bail out smaller defenders switched onto big men during the pick-and-roll. A defending big will come over and relieve the smaller defender, who will retreat to the perimeter. This scram is a funny example because it’s actually Jrue Holiday, another guard, coming over and saving Payton Pritchard from certain death in the post (although, with this sad excuse for an entry pass, maybe Pritchard would’ve been just fine on his own):

You could write a book on modern defensive principles; we’ve only scratched the surface here. The history of NBA defense is long and winding, doubling back on itself time and again, but inevitably moving forward. Like chefs remixing classic dishes with modern ingredients, coaches are always cooking up something that looks new but contains hints of the old. If we look hard enough, we’re all in for some tasty meals in the coming years.