Team Ratings: What They Mean, Why They Matter
We’ve witnessed quite a few close wins and nerve-wracking finishes in the first month of the WNBA season. With this in mind, how heavily should we rely on win-loss records when it comes to evaluating team performance? After all, if one team beat another by just one point, should we expect the same team to win the next time they play?
Of course, the answer is no. Margin of victory, the difference between the points scored by the winning and losing team, is an important metric to consider when analyzing team performance. It is a far better predictor of future performance in sports than record.
Margin of Victory per 100 Possessions (Net Rating)
When we are evaluating a team’s margin, an important consideration is their pace of play. The Las Vegas Aces lead the WNBA with 84.3 possessions per game while the Sparks are the slowest paced team at 78.1. That means the Aces go up and down the court 8% more often than Los Angeles. To control for that, it’s far better to measure a teams margin of victory per possession rather than per game. We’ve charted each team’s net rating below.
The Connecticut Sun and Seattle Storm are the clear leaders so far this season by margin of victory per possession. However, they are currently fourth and third in the standings respectively. The top two teams by record, the Phoenix Mercury and LA Sparks, appear to be in something of a next tier. As an example of the value of looking at margin, the Mercury are 4–0 in games decided by 6 points or less so far this season. It will be hard for them to remain undefeated in such close games the rest of the way.
In a similar vein, the Minnesota Lynx rank eighth in win-loss record. However, they are vying for the sixth spot by net rating so far this season. They lost their opener by just one point to the Sparks and also have a two-point loss to the Atlanta Dream. Flip one of those games and the Lynx would be just half a game out of the playoffs.
Offensive and Defensive Efficiency
One way we like to visualize net rating is to break it down into it’s two primary components: points scored per 100 possessions (Offensive Rating) and points allowed per 100 possessions.
The chart is a two-dimensional way to look at net rating. As the label indicated, the further down and to the right a team appears, the better it’s margin of victory. As a result, the graph is slightly more complicated but has the benefit of revealing what is driving a team’s performance.
For example, we can see that the Sun combine the second best offensive efficiency (far to the right on the graph) with one of the better defenses in the WNBA (only three teams are below Connecticut, meaning they have been more stingy). We can also see that the Washington Mystics are playing well on offense but have been second worst in the league at getting stops. If they can improve their defense and move down the graph, they’ll rank higher by net rating. The graph also highlights that the Dream are staying around 0.500 with the worst offense and best defense so far this season.
Our goal with this post was to introduce these charts and explain how to read them. We’ll be updating the graphs regularly this season on Twitter, Facebook, and Instagram. We hope you’ll find them useful, and please let us know if you have any questions.
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