Impact of Zone Defense

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This article (courtesy of Truehoop) got me thinking. Now it’s obviously pretty heavily biased. It’s a Kobe fan’s attempt to universally declare the players of this era (say the last 5 years) better than all previous and to establish that today’s players suffer under rules and styles that impair their ability to amass stats. That said, he did some good research.

The problem with his conclusion, other than the fact that he made it before he began checking the facts and interpreted everything through obviously biased lenses, is that he used only total points and field goal percentage to measure the impact of zone defense. He did not take into consideration other changes in play style. Scoring went down in the late 90’s because the pace diminished. This was a coaching choice. No rules changes took place to inhibit scoring. That said, teams became more focused on effective scoring through getting to the free throw line and shooting the three pointer. This trend continued over the years.  Effective field goal percentages actually went up dramatically after the zone defense went into effect.

Year eFG%
1984 0.495
1989 0.489
1994 0.485
1999 0.466
2004 0.471
2009 0.500

It’s not hard to see why eFG% jumped up either. Watch Dwyane Wade attack helpless perimeter players and get to the paint or the foul line at will in the 2006 NBA Finals because the no handcheck rule, coupled with the defensive three second rule that keeps shotblockers out of position, made explosive slashers almost indefensible. Watch Shaquille O’Neal become ineffective in those same finals because the zone defense has a massive impact on post players who can be doubled and hedged before they even catch the ball now. Watch the 2007 NBA Finals and witness the exact same thing happen for Tony Parker and Tim Duncan.

It’s clear from the MVPs of the last decade as well.

Before Zone / No Handcheck rules took effect 2000-04 MVPS: Shaq, Iverson, Duncan, Duncan, Garnett. It’s all big guys except Iverson, who realistically probably should have lost to Shaq or Duncan if you went by objective standards.  Actually going back through the ’90s the best players were always bigs with one exception.  Michael Jordan.  Other than him your MVPs were Barkley, Hakeem, Robinson, and Karl Malone in the ’90s.

Since Zone / No Handcheck took effect 2005-09 MVPS: Nash, Nash, Nowitzki, Bryant, James. It’s all perimeter players. Even Dirk is a perimeter player on offense.

It’s pretty clear both by the numbers and by observation that the zone inhibits interior scorers and the handcheck enables perimeter scorers. Why did scoring numbers and shooting percentages dip between the late 1980s and the rules change in 2004? Style of officiating and play and a preponderance of great big players that allowed teams to play better ball when they slowed it down and played through the post – Shaq, Hakeem, Robinson, Ewing, Malone, Barkley, Mourning, Duncan, Webber… It was just the times. Riley started it in the early ’90s, using a physically pounding style to grind a superior Bulls team to 7 games in the Eastern Conference Semi-Finals in 1992. It caught on. It got worse. Pace diminished. Offenses were stalled by design and shooters had to contend with a ton of physicality.  The most effective way to score was in the post (the high post if you had MJ).

The other thing that was not examined in terms of statistics accrued is the effect of Usage.  Yes the pace slowed, but did the Usage rates of stars remain constant?  Not even close.  31 of the top 100 Usage rates* since 1972 come after the introduction of the zone defense.  That means that while these players may not play in an era with a lot of possessions, they use more of them than older generations did.  This makes sense since fewer possessions indicate that the game is being played at a more reserved pace and the ball can be force-fed to the best scorer on the team more often.  Further 50 of the top 100 Usage rates come from 2000 and after, indicating that this issue may be completely unrelated to rules.  It is likely a stylistic choice by coaches as part of the natural evolution of the game.

One way of examining the production of players without pace being a factor is look at metrics that are based around possessions played, like PER.*  Looking at the top PER seasons since 1980 we see a nice mix through the years.  If any seasons seem to be missing it’s certainly not the post-Zone era.  Plenty of players in that range are high up the list including LeBron, Wade, Paul, Garnett, and Dirk all in the top 30 (and Kobe at 31).

There’s no way to determine that one era of players is unilaterally better than another era of players by anything as simple as a comparison of shooting percentages and a few interviews. In terms of skill and athleticism of course the game evolves, but it’s pointless to compare across generations without a sense of historical perspective. If you gave players from the past, even the likes of Bill Russell or Elgin Baylor, the advantages in training, skill development, nutrition, travel, and strategy that we have today, you don’t know what you’d have. Similarly, who knows what kind of player Wade or Bryant would be if they grew up in the ’50s, prior not only to Jordan, who clearly inspired their games, but prior to Jordan’s inspirations – Dr. J, David Thompson, Jerry West.  They would have to be innovators and might be giants in the game’s history, but what they would not be is the players they are today.  The comparison is simply not apples to apples.

*Stat lists include only player seasons with at least 41 games played and an average of 24 minutes per game.

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