Illegal Defense in the NBA

As anyone that knows me, I talk often about NBA rules and their differences vs. other leagues/levels. It's not uncommon to be watching a game with friends and have them yelling at the tv screen. In most cases, what they're upset about is what they deem to be a foul or violation. Depending on the friend, sometimes I bite my tongue and don't say anything. Other times, though, the explanation is simply that the NBA has its own set of rules. 

One of the rules that fascinates me is "illegal defense" or "defensive three seconds." Both are synonymous and mean the same thing. Put simply, illegal defense is called when a member of the defending team spends more than three seconds in the free throw lane while not actively guarding an opponent.

A Brief History

In January of 1947, the NBA banned zone defense in an effort to promote the natural flow of the game. At the time, the three point shot didn't exist, and the league was afraid that teams would simply "pack it in" on defense and force their opponents to only shoot jump shots. 

The option to play zone wasn't re-introduced back into the NBA until the 2001-2002 season. So while other players and coaches were used to zones in leagues around the world, it was never a part of the fabric of the NBA. 

While man to man defense is all that could be played, coaches were smart and started playing guys in gaps and using their big men to help. This led to the illegal defense rules of the 1990's, which we'll discuss in a minute. 

Illegal Defense in the 1990's

The illegal defense rules of the 1990's were put in place to combat some of the changes that coaches were making to help out on post ups and isolation plays. A dominant big man (or isolation player like Michael Jordan) at that time would catch the ball on the block and essentially go to work unless an opposing coach brought help. 

So, here is what was introduced: 

1. Defensive players had to play man-to-man or double team. There would be no hedging or playing in between your ball and your man.

2. If an offensive player caught the ball on the left block and his teammates all spaced out around the three point line, the defenders had to be above the free throw line or on the other side of the center line. 

Here is what that looked like in action: ​https://streamable.com/u4egnw

This led to a lot of isolation or two-man basketball, with John Stockton and Karl Malone being two of the great beneficiaries. The offensive 5-second call was also introduced to prohibit post players from taking forever to back down their man. 

Karl Malone benefitting from the 1990's illegal defense rules.

Did teams still hedge? Of course they did. Both the Bulls and Sonics, two of the elite defensive teams in the 90's, played a lot of gap defense and forced officials to make judgement calls. When former Sonics coach, George Karl, published his book, Furious George, in 2017, he actually brought it up: 

“Hell yes, we played a zone. A lot of teams played man-to-man on the strong side…and zone on the weak side.”

The Illegal Defense Rule Change in 2001-2002

​​In 2001, the NBA's owners approved four rule changes in the hopes of improving the "flow and pace" of the game. The most significant of those rules was defensive three seconds. Former Suns coach Paul Westphal, who was on the competition committee at the time, said the rule was designed to help teams that lacked a dominant big man.

According to the NBA rule book, the count for defensive three seconds starts when the opposing team is in control of the ball in the front court. It's stopped if one of the following happens:

A player is in the act of shooting.
There is a loss of team control.
The defender is actively guarding an opponent.
The defender completely clears the 16-foot lane.
It is imminent the defender will become legal.
​
Critics of the rule were worried that it would shrink the court. By allowing teams to play more zone, help freely, and drift from non-shooters, dribblers wouldn't have any space to get to the basket. 

Interestingly, over the next ten years, the pace of play did get worse. In fact, the average number of possessions per game was at an all-time low from 2001 to 2010 according to Basketball Reference. Teams could take away a dominant player more easily, and the guys that had been accustomed to isolation dominance suddenly faced a new challenge. 

How it Changed the Game

​When the NBA introduced the rule, they envisioned a league of scoring where players moved up and down, took a lot of shots, and played at an entertaining pace. While it's a fair argument to say that the rule hurt the league for many years, we wouldn't be where we are today without it. 

The NBA defensive three second rule forced players to evolve. It bred guys like Steph Curry and perimeter sharp shooters. Being able to score in isolation on the block all of a sudden wasn't so important. To play in the NBA, you needed to be able to spread the floor. Big men learned to adeptly pass out of the post when double teamed. Shooters learned to space and create angles for the passer. While the pick and roll is still popular, it's a lot harder to execute now when help-side defenders can move over to defend. 

How Defenders Have Evolved

With any rule, coaches and players eventually figure out ways to exploit gray areas. A couple examples: 

Guarding the Player With the Ball

A defender is allowed to sink in the lane when his man has the ball. Take a look at the example below of LeBron James guarding Ben Simmons. Once Simmons passes the ball, James has to go back to him. 

Cleansing

This refers to a defender touching an opposing player as they cut through the lane. A big man, for example, may make slight contact with a guard cutting out to the wing. The slight touch resets the three seconds because the big man was "guarding" the other player. We see players like Nikola Jokic and Brook Lopez do this quite well. 

The 2.9

Many big men will hang out in the lane as long as possible and then take a step out at 2.9 seconds to avoid getting called. Many NBA assistant coaches work with big men to establish these types of movement patterns so it becomes second nature. 

Final Thoughts

The NBA is a business, and every business is always looking at ways to improve its product. The illegal defense rule, though, has remained consistent since it was passed. With the types of players in the league today, the rule has aged well and done a nice job of providing defensives flexibility without being too disadvantageous to the offense.