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The Evolution of the NBA, Part Two

NBA Statistical Analyst Kevin Pelton

by Kevin Pelton, 6/12/06


In the big picture of the NBA, the story of the 2006 Playoffs remains the league's evolution and the impact of the league's effort to promote a more exciting brand of basketball and increase scoring. It's a subject I touched on to some extent in my last column in this space, but there the focus was more on how we perceive the change than what caused it and what it means.

Shortly thereafter, respected NBA writer David Aldridge (always one of my favorites) wrote an influential column in the Philadelphia Inquirer entitled "Trend in NBA favors offense."

"For the last two decades, just about every team that has won the NBA Finals has been the league's best defensive team," wrote Aldridge. "And on that team there has been a player - or players - considered among the best defenders at his position.

"The '80s Lakers had Michael Cooper. The Celtics had Kevin McHale and Dennis Johnson. The Pistons had Dennis Rodman and Joe Dumars. The Bulls had Michael Jordan and Scottie Pippen - and, in their second Threepeat, Rodman. The Rockets had Hakeem Olajuwon. The Spurs had David Robinson and have Bruce Bowen. And the new-millennium Lakers had Kobe Bryant and Rick Fox.

"Which is why this season, in so many ways, represents a sea change in the NBA."

One way to test Aldridge's assertion is to look at where the eventual NBA Champion ranked in the league in Defensive Rating during the regular season over the last 20 years. Here's what that chart looks like:

Yr  Team  Rk    Yr  Team  Rk
------------    ------------
05  SAS    1    95  HOU   12
04  DET    2    94  HOU    4
03  SAS    3    93  CHI    8
02  LAL    7    92  CHI    4
01  LAL   19    91  CHI    6
00  LAL    1    90  DET    1
99  SAS    1    89  DET    3
98  CHI    3    88  LAL   11
97  CHI    4    87  LAL    6
96  CHI    1    86  BOS    2

Now, let us note that there is a significant leap of faith between a team's defensive ranking and their true defensive ability. Does anyone think that the "Lightswitch" 2000-01 Lakers were really a below-average defensive team? Nah; they just didn't turn it on until the postseason.

That said, the league's top-rated defensive team has won the championship five times in the last 20 years. The eventual champion has been in the top three in Defensive Rating 10 times and top five 13 times. Still, there are a number of teams that won at least as much as on the strength of their offense as their defense.

I can predict with Kreskin-esque accuracy that this year's champion will be either Dallas, which ranked 11th in the NBA in Defensive Rating, or Miami, which ranked ninth. Are these two teams poor defensively relative to past champs? Sure, but they are not so out of place on this list that it is obvious something has changed. The most similar teams to the Mavericks in terms of Offensive and Defensive Ratings compared to league average were the '80s Celtics and Lakers.

There's another part of the argument that offense has become more important that just doesn't fit. If Dallas and Miami reaching the Finals this year proves the game has changed, what are we to make of last year, when supposedly traditional powers Detroit and San Antonio squared off on the game's highest stage? After all, as I've pointed out before, the game changed last year, even if it wasn't as clear as it has been in this year's postseason.

Maybe a chart will help better understand where the NBA game has come from and is going. The following chart plots league-wide Offensive Rating and pace for the last decade:

Note, first, that when the evolution of the NBA is ascribed in part to the legalization of zone defenses prior to the 2001-02 season, this is probably a stretch. That change briefly arrested and in fact reversed the trend of declining Offensive Ratings, but had limited long-term impact. The same cannot be said of the rules interpretations limiting contact on the perimeter prior to last season.

While we are here, make note of the fact that this was not a rules change; it was a re-interpretation. The WNBA, in enacting the same change prior to the 2005 season, made this very explicit in a story on WNBA.com. (Incidentally, the change in enforcement was not nearly as dramatic in the WNBA as in the NBA.)

This is more than an issue of semantics. There are critics who will argue that the NBA has created an "impure" game over the last two seasons, but they ignore the fact that rules limiting hand-checking have been on the books for more than a decade, since the New York Knicks did everything short of mugging opposing guards en route to the 1994 NBA Finals. Over the following decade, enforcement became progressively less strict before the NBA stepped in during the summer of 2004.

Over the last two years, the new rules interpretation have increased offense in two ways -- by sending players to the free-throw line more frequently and offering more open shots. This is evident when we look at two measures, the number of free-throw attempts per possession and effective field-goal percentage:

Yr FTA/Ps  eFG%
---------------
04  .270   .471
05  .288   .482
06  .292   .490

That offense has gone up, however, is unquestioned. What is a more interesting question is whether this makes offense more important, as Aldridge and many others have asserted. On its face, this argument does not make sense to me. If "the new NBA" features more penetration and it is more difficult to contain on the perimeter, doesn't that make it more important to play good help defense and have shot-blockers on the interior? Just because there is more offense does not make it more important. For example, Offensive Ratings are higher in the NBA than in the WNBA. Would you take that to mean defense is more important in the WNBA?

One way to evaluate the relative importance of offense and defense is to look at the correlation between Offensive Ratings and Defensive Ratings and team performance league-wide. That is, how well do Offensive and Defensive Ratings predict team performance in a given season? And which shows as being more important in a given season?

Here are these correlations for the last 10 seasons, along with which end of the floor was more important that season:

Yr  OCor   DCor  ?
------------------
97  .824  -.875  D
98  .814  -.768  O
99  .621  -.751  D
00  .739  -.823  D
01  .810  -.727  O
02  .794  -.669  O
03  .788  -.584  O
04  .576  -.630  D
05  .733  -.666  O
06  .578  -.622  D

Remarkably, this year's correlations are virtually identical to those from 2003-04, the year before the new rules interpretations.

What about the playoffs? Well, really we're talking about two series here - Dallas over San Antonio and Miami over Detroit. It is tough to read too much into the Miami-Detroit series from this perspective, because the Pistons were both the better defensive team and the better offensive team. Detroit's offensive makeover this season seemed perfectly suited for a freer-flowing offensive NBA, but that fell apart when Rasheed Wallace hurt his ankle against Cleveland.

How about Dallas-San Antonio? In my last column, I cited this as a tipping point of sorts for the evolution of the NBA, but this was really my read on how the NBA as a whole perceived it, not my own take. Do I think San Antonio would have won the series had it been played pre-rules re-interpretations? Yes, probably, but the Mavericks are a good team regardless of how the game is played, and they beat San Antonio in overtime of the seventh game of a series where five of the seven games were decided on the final possession of regulation or in overtime. Sorry, but that's not enough for me to declare that the NBA has changed.

It remains true now, just as it was two years ago, just it was a decade ago, just as it was when Dr. Naismith invented the game, that the best basketball teams have good offenses and good defenses. No rules interpretations can change that.

So if offense hasn't become more important, what are the implications of the evolution of the NBA? We'll take a look at that in a future column. Stay tuned.

SBL Appearance

Last Thursday, Jamie Mottram was nice enough to have me as a guest on Sports Bloggers Live. Unfortunately, the content -- previewing the NBA Finals -- is now a bit dated, but you can listen to the segment here if you are perchance so inclined.

Mailing List

My writing for this site and SI.com follows no regular schedule. If you'd like to be notified when I've posted a new column, please e-mail me at kpelton@hoopsworld.com.

Kevin Pelton formerly wrote the "Page 23" column for Hoopsworld.com. He provides original content for both SUPERSONICS.COM and storm.wnba.com, where you can find more of his analysis of both the NBA and the WNBA. He can be reached at kpelton@hoopsworld.com.

Also see Kevin's previous columns for 82games.com:
The Year in Stats
Why I'm an APBRmetrician
Wanted: Open Minds
Investigating Dwyane Wade's Injury Risk
The Similarity of Eddy Curry and Mike Sweetney
Rating the Rookies: Projected Fantasy Stats
Valuing the Preseason
Every Play Counts: Kobe Bryant
Comparing the 50 Greatest
Every Play Counts: The Phoenix Pick-and-Roll
Every Play Counts: Antonio Daniels
Every Play Counts: Detroit-San Antonio
The Value of Kobe Bryant
Every Play Counts: The Phoenix Suns D
The Value of Steve Nash
The Curious Case of Darko Milicic
The 2005-06 Every Play Counts All-Defensive Teams
Playoff Predictions
Playoff Thoughts
Every Play Counts: Kobe Bryant v. Raja Bell
The Evolution of the NBA


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