By Julian Ryan
The current San Antonio Spurs team, despite winning the NBA Finals in a dominant fashion, are getting some flak from the internet community for being too old and past their prime. Even the statistical community is predicting some slippage for Greg Popovich’s warriors. This begs the question: how old is too old and are the Spurs past it?
To answer this, I looked at each team’s regular season performance from the last ten years and calculated their average age, weighted by minutes played, and win total, prorating to an 82-game season where appropriate. I then regressed wins against average age and average age squared, and indicators for each team to account for some teams having been better over the past decade.
The coefficients on age and age squared were +35.35 (s.e. = 9.5) and -0.594 (s.e. = 0.177) and both were conclusively statistically significant. The signs of the coefficients imply a quadratic relationship as was somewhat to be expected. Older players tend to be more experienced and better, but there comes a point where athleticism begins to decline and this outweighs the gains in experience. Below is plotted the expected win total in an 82-game season, for the average NBA team:
So what is the optimal age for an NBA team? According to these coefficients, the ideal average age of a team is 29.8 years. The only teams over this threshold last year were the Mavs at 30.6, the Nets at 30.0 and indeed the Spurs’ finals opponent Miami at 30.6, just barely the second oldest team in the league last year.
All of those teams won over half their games and in general older teams have tended to perform better. Almost all teams are younger than peak age, likely because older players cost more and thus cannot be fit underneath the salary cap. As for the Spurs last season, buoyed by the youthful Kawhi Leonard, they came in fourth with an average age of 28.9. That number rose to 29.6 in the playoffs as Duncan and Ginobili got more minutes, placing them right at the perfect age for a team.
So will the Spurs be too old going forward? It seems unlikely. They basically return the same roster this year and so projecting to be one year older for an average age of 29.9. That said, they will probably skew slightly younger as Popovich continues to shift minutes away from the old guard to his younger talent. So the Spurs aren’t too old, they’re hitting their peak. Cleveland, playing in the East, are perhaps the favorites; but San Antonio should be right there again.