Learn a Stat: Team Offensive, Defensive, and Net Rating

Welcome back to Hack a Stat! This is a new chapter of the Learn a Stat: after knowing about possessions and Pace, today we will discover team ratings: Team Offensive, Defensive, and Net Rating. As you will see, they are advanced statistics that are very easy to calculate but offer valuable information about teams’ offensive and defensive phases.

ITALIAN VERSION

OFFENSIVE AND DEFENSIVE RATING

Introduction

When we look at a box score, the first thing we read is the final score: it is the most important information since it allows to understand who won. The points scored, however, do not give a clear vision of the game, but only partially. They don’t give us information about game quality, for example. Or, again, if that score is the result of a high or low pace.
The pace in fact influences all the statistics, above all on the score. Here then statistics such as Offensive and Defensive Rating allow us to understand the team’s offensive and defensive quality, which is impossible with the score alone.

Definition

The Offensive and the Defensive Rating are the values that show the points made (Offensive) and allowed (Defensive) by a team on a basis of 100 possessions.

These two statistics, therefore, allow comparing the points scored and allowed by teams that play at different paces, thanks to redistributing the points over 100 possessions. Redistribution on possessions is very important: depurating the score from game speed is the first step to a uniform comparison of offensive and defensive skills. But above all it allows us to understand the quality of the game.

Formula

Both formulas come from these proportions:

So the formulas are:

The points (made or allowed) per one possession are calculated and then multiplied by 100, in order to have easier-to-read numbers.

Both formulas can be used both with the values of the single game or with the average values of a season (or part of it); the only important thing is to use the possessions corresponding to the reference period.

When calculating the Team’s Offensive Rating for a single game, the value coincides with the opponent’s Defensive Rating. Consequently, the League averages of the Offensive Rating and the Defensive Rating will be the same.

Let’s see how can you read team Offensive, Defensive, and Net Rating.

As for Pace, for these statistics there are no limits or range of values that tell us uniquely how a team plays: depending on the values of the entire League it can be understood which team plays good or bad. Example: in the 2016/2017 season the best Italian team in Offensive Rating was Milano with 114; the average for Serie A was around 107. In Euroleague, on the other hand, the average was around 112 and with an Offensive Rating of 114, you are closer to half of this ranking and not to the top.
In any case, the basic rule always applies: the higher the Offensive Rating, the better the offensive production; the lower the Defensive Rating, the better the defensive production.

Previously we told about offensive and defensive quality: in the formula of possessions, the total shots and the turnovers are counted. When the points made or allowed are divided by this value, the Rating is calculated taking these factors into account and therefore the result depends on them. This is why it can be said that the ratings manage to highlight the playing quality (ie an offensive game with a few turnovers and good shooting percentages); an equal talk can be made for the defensive quality, where the number of missed shots and the turnovers by the opponent tend to indicate the skill of the defense. Here is a practical example.

Let’s compare two hypothetical games with identical scores. In addition, the teams scored the same number of shots of 1, 2 and 3 points. The difference lies in the percentages: Venezia and Sassari attempted more conclusions than the other game; they also more turnovers. These two factors obviously affect the number of Possessions.

How will all these factors affect the Offensive Rating?

Fewer turnovers and missed shots are equal to higher offensive quality. Therefore, with the same score, Milano and Trento will have created a higher quality game with fewer mistakes; the second game is heavily conditioned by missed shots and lost balls: the score does not reveal this aspect, while the Rating does. When you come across two games with the same score, it is good to calculate Pace and Rating in order to have a more complete picture.
Furthermore, thanks to the Offensive Rating, we can compare the attacks of the four teams even if they played at a different pace: in this case, Trento was certainly the most productive.

Another example: in this case, we have different scores, but equal Offensive Ratings.

Obviously, if we have the same Ratings the difference is created by the number possessions; but how is it possible that two teams that have scored more than 100 points have the same Rating as two teams that have made less than 90 instead? Simple, Milano and Trento will have scored a lot, but they have more turnovers.

This affects the possessions, the Pace and the Offensive Rating too. This example shows us how observing the Offensive Rating alone is not enough to understand the game quality, but we must look at traditional statistics and Pace.

The next step is the Net Rating.

NET RATING

Definition

The difference between Offensive and Defensive Rating provides the Net Rating that is the difference in score spread over 100 possessions. Clearly, the Net Rating of a single game will be positive in case of victory, negative in case of defeat. If it is calculated on the whole season, it will be positive if the team has achieved more wins than losses, negative in the opposite case.

Formula

It is one of those statistics that say everything and nothing: surely the comparison of the Net Ratings allows understanding which are the most powerful (those with the highest Net Ratings) compared to the others. But by observing only this data, other aspects are lost, such as offensive and defensive quality.

This Learn a Stat ends here. Now you know everything about team Offensive, Defensive, and Net Rating. See you soon, your friendly neighborhood Cappe!