Nov 9, 2014; Portland, OR, USA; Denver Nuggets head coach Brian Shaw looks on as the Nuggets play Portland Trail Blazers at Moda Center at the Rose Quarter. Mandatory Credit: Jaime Valdez-USA TODAY Sports
As the understanding of analytics has built, teams, fans and media have gradually moved away from per-game measures of performance, particularly at the team level. We understand that judging two offenses by their points per game averages is an imperfect comparison because it doesn’t account for the pace each team plays at, and the number of opportunities they have to score those points within each game. Thus, a possession has become the common denominator for many of the most widely used basketball statistics. We now, generally, compare offenses based on efficiency—leveling the playing field of pace and looking at how many points they score or allow per 100 possessions instead of per game.
However, this can create something of a cognitive illusion because games—wins and losses—aren’t measured 100 possessions at a time. The parameters of a game are still chronological. Each team is given 48 minutes to outscore the other. What they do with that 48 minutes is up to them and doesn’t necessarily match the processes of their opponent.
Take, for example, the Denver Nuggets. Through their first 18 games the Nuggets have an even nine wins and nine losses. According to Darryl Blackport’s game logs, they are also exactly even with respect to point differential. They have both scored and allowed 1,894 points. However, their Net Rating (per 100 possession point differential) is -0.9. This indicates that all things being equal, if the Nuggets and their opponent were allotted an equal 100 possessions in each game they would, on average, lose by about a point. This may seem incongruous. How can a team with a negative efficiency have scored exactly as many points as they’ve allowed?
The answer is the denominator of possessions and the fact that the Nuggets have had more of them than their opponents, 10 more offensive possessions to be exact (this data can be found in Blackport’s game logs as well). That differential is the largest in the league so far this season.
We generally think of possessions as being equally distributed in a game, since possession is a binary scenario. One team has the ball, then the other. There is no third condition. Each team gets the first possession for two quarters of a game and that binary nature should create equal opportunities. However, the chronology of a game throws a monkey wrench. Games are divided into quarters which end after 12 minutes, not when each team has had an equal number of shots. Either by accident or by intention, teams can gain as many as two extra possessions over the course of a game by ensuring that they have the last possession in a quarter.
There is one important distinction to be drawn with this idea of creating extra possessions. Generally, speeding up the pace is a losing proposition for an underdog. If you are worse than your opponent on a per possession basis, creating more possessions means more opportunities for that difference to manifest and less opportunity for the effects of random chance to work out in your favor. But what the Nuggets are doing is not necessarily speeding up the pace and creating more possessions for both teams, they are exploiting the clock to create more possessions for themselves only.
The fact that the Nuggets have such a wide possession margin would seem to indicate an intentionality. Working for two-for-one opportunities to give themselves extra possessions works in their favor, although the rushed circumstances of possession trying to take advantage of this opportunity may decrease the expected value. While that possession margin is what makes their efficiency negative—since they scored the same number of points as they allowed, but needed more possessions to do it—more offensive possessions allows them a slim chance to overcome that negative efficiency within the confines of a 48-minute game. Essentially, they score slightly less per possession than their opponents do. But they give themselves more possessions per game, which wipes away the difference.
This loophole the Nuggets have found and exploited has always existed within the structures of the game and they are not the first to try and take advantage. Every team does it to some degree and, over the course of the season, the Nuggets’ possession margin may shrink (biggest possession margin in the league last season was +19 by the Philadelphia 76ers). In the end it tells us a very small bit about the Nuggets process, and offers a reminder that understanding how basketball metrics relate to wins and losses often means understanding how the metrics relate to each other.