The First 50 Games: Spurs and Warriors on an Unprecedented Run
Since late October, we’ve marveled at the seemingly unprecedented dominance of the Golden State Warriors and, to a lesser extent, the San Antonio Spurs. We’ve focused specifically on the Warriors’ unstoppable offense and the Spurs’ impenetrable defense. On the flip side, we’ve also followed the abysmal results plaguing the Philadelphia 76ers and the Los Angeles Lakers. With roughly 60 percent of the NBA regular season complete, it’s an opportune time for us to examine how these and other performances stack up historically.
This analysis takes a snapshot of every team’s offensive, defensive, and net ratings through the first 50 games. It extends all the way to the 1983-84 season — the farthest back that Basketball Reference has such data. The objective is to see whether the NBA has previously had a year with two superpowers, two extremely challenged franchises, or both.
Let’s start with net ratings (scroll to the right and note the blue dots):
As these boxplots show, we seldom see teams separating themselves from their competition in ways that might be described as “outlier”[1. In this analysis, I use John Tukey’s definition for suspected outliers, which is 1.5 times the interquartile range above the third quartile or below the first quartile. It’s a conventional but by no means conclusive approach.] performances. Yet, this season, both the Spurs (+14.5) and Warriors (+12.6) have notably outpaced the league. There have certainly been other great tandems (e.g., the 1986 and 2009 Lakers-Celtics rivalry), but their dominance was not to the same degree as what we’re witnessing today.
On the other hand, although the Lakers (-10.9) and Sixers (-11.0) have been miserable this year, they’re nowhere near the futility of the 1993 Mavs (-16.9) and the 2012 Bobcats (-13.9). They’re actually similar to the Bulls (-10.4) and Clippers (-11.1) from the 2000 season in terms of raw net ratings. But, since teams back then were slightly less spread apart than they are today, the Bulls-Clippers tandem is technically “suspected” as an outlier while the Lakers-Sixers tandem is not. The differences are minute, though, so we shouldn’t be too dogmatic in how we interpret the data.[2. The Lakers and Sixers are within 0.3 of the suspected outlier region — literally right at the cusp.] The bottom line is that, for only the seventh time, we have a pair of teams with net ratings below -10, and they have never been as far behind the top two as the Lakers and Sixers are right now.[3. The other six seasons are 1989, 1990, 1995, 1996, 1998, and 2000.]
The gap between the haves and have-nots is particularly evident on offense. Once again, the Lakers and Sixers markedly trail the league, which has the Warriors and Spurs at the top. But, this time, the two superpowers are joined by the Oklahoma City Thunder, whose 113.2 offensive rating ranks second. The only other time we’ve seen this kind of split among multiple teams is 2003, when Denver, Cleveland, and Miami were below 98 while Dallas approached 112.
Defensively, the Spurs are the sole team of distinction. It harkens back to their 2004 to 2006 seasons, when they boasted the lowest defensive ratings in the NBA. Overall, in these charts, they stand out for their excellent play on both sides of the ball.
We can, of course, perform other types of analyses to gauge the relative strengths and weaknesses of teams historically.[4. For instance, we can compare “adjusted efficiency” ratings, as Andrew Lynch and Ian Levy did in this February 2014 analysis. We can also calculate z-scores — a fairly common approach that’s been applied not just in basketball, but also in baseball, football, and other sports. I actually tried both methods and found results similar to those above.] This is hardly definitive, as there’s no attempt to account for strength of schedule, home-court advantage, and other factors through the first 50 games. Nevertheless, it helps reinforce how unique the 2015-16 season is and why we should appreciate what’s in front of us.