As stated in the about page here, part of the goal of this blog is to explore a new metric for analyzing NBA teams. Below I will explain how the new statistic functions in the modern NBA.
Before explaining this new metric, it is important to understand the variety of stats that need to be used. The first broad stat that needs to be understood is “Net Rating.” Net Rating was a metric developed by Dean Oliver in his book Basketball on Paper. What it calculates is, over the course of one hundred NBA possessions, the point differential between “Team A” and “Team B”. This is important because, in today’s NBA, you have teams like the Golden State Warriors who play at a much faster rate than the rest of the league. This results in the Warriors having more offensive possessions than any other team in the league. Thus, using a simple point differential statistic would result in a biased view that prefers the Warriors style.
The way Net Rating is conducted is by using two individual metrics: “Offensive Rating” (known as ORtg) and “Defensive Rating” (known as DRtg). The formulas for calculating each statistic are complicated, and beyond the purpose of this blog; however, if you are interested a detailed breakdown can be found here. Overall, the calculation for “Net Rating” is simply done by subtracting defensive rating from offensive rating. So, for example, let’s say Team A’s Offensive Rating is 100. Meanwhile, their Defensive Rating is 75. Their Net Rating would thus by +25.
The second important stat for this blog is known as “Offensive Effective Field Goal Percentage” or Offensive eFG%. Additionally, the third and final crucial statistic is “Defensive Effective Field Goal Percentage” or Defensive eFG%. To understand eFG%, knowledge of simple Field Goal Percentage (FG%) is necessary. Essentially, FG% looks at every shot “Team A” takes and calculates the percentage made. So if “Player A” takes twenty shots, and makes ten of them, his FG% is 50%. What eFG% does, though, is weigh a three-point field goal more than a two-point field goal. Thus, it calculates the efficiency of shots taken. The formula for this is: “(FG +.5 *3P)/FGA. Thus, if “Player A” takes twenty shots, makes ten of them, and five of the made shots are threes, the formula would read: “(10 + .5 * 3)/20” = 57.5%. On the other hand, Defensive Effective Field Goal Percentage is, essentially, what “Team A” allows its opponent’s eFG% to be. When both are considered we will call it “Optimal eFG%.” Overall, this statistic adjusts for the fact that a 3-point field goal is worth one more point than a 2-point field goal.
Now that I’ve explained the three necessary statistics, it is time to answer why this is important. I was recently watching the Spurs play the Celtics and was amazed that, in the second quarter, San Antonio were beyond dominant; however, in the fourth quarter they were not playing the same sport as Boston. This led me to think, “who is the most dominant team when they are playing at their average or better?” This is a stat that has been examined broadly – from game to game – however, that does not look at how dominant teams are in parts of games. For example, the New Orleans Pelicans recently defeated the Cleveland Cavaliers. If you look at the overall game statistics, the Cavs had a significantly lower than average Optimal eFG%. Thus, why did the game go into overtime? If you look at the game, quarter-by-quarter, during the fourth quarter the Cavs shot well above their Offensive eFG% and defended well beyond their average Defensive eFG%. This resulted in a +31.9 Net Rating. Therefore, the metric this blog will advance takes into consideration a team’s average Offensive eFG% and Defensive eFG%.
After looking at those numbers, we look at quarters where said team shoot’s at or above their Offensive eFG%, defends at or above their Defensive eFG%, or both. Finally, in those quarters where a team does one or all of the above, we will look at the Net Rating. When a team accomplishes a quarter at or beyond their average Offensive eFG% and Defensive eFG% this metric will be known as the Dominance Metric and will examine how dominant the dominant teams are when they are playing basketball at an average and/or beyond-average level.
Thus the goal of this website is, over the course of time, to bring the reader statistical-driven analysis of a variety of sports. If anyone cares to send feedback to the author, you can contact us at firstname.lastname@example.org or on Twitter at @sports_by_stats.