There are many ways of attempting to calculate the impact of a player being on or off the court. One method is to calculate team offensive and defensive ratings when the player is on and off the court. This allows players across teams to be compared independent of how good the team is. If a player’s team has poor ratings, but performs even worse without her on the floor, these calculations can show her positive impact. Similarly, players on good teams will generally have solid ratings, but the team might not be playing much better with her on the floor. Like all methods, this is not a perfect way of measuring a player’s impact as it is affected by other factors, like the other players in the lineup and the different nature of garbage time.
All players who only appeared for 1 team this season and played at least 680 possessions, which is 20 per game played by the team, were included in the calculations. The offensive chart includes all players whose on-court offensive rating was at least 5 points per 100 possessions better than the team’s offensive rating without the player on the court. The defensive chart includes all players whose on-court defensive rating was at least 6 points per 100 possessions better than the team’s defensive rating without the player on the court. Each chart includes the difference in the rating when the player is on and off the court and the approximate percentage of the team’s total possessions when the player was on the court.
All stats are from wnba.com and calculations involved are subject to rounding and estimation.
The most obvious observation from the look at the offensive ratings is the excellence of the Los Angeles offense when the starters are on the court as the four players who play the most were among the top five in this category. While the impact of all five starters were noticeable, the top two players, Kristi Toliver and Nneka Ogwumike deserve special mention. The Sparks scored more than 50% more points per possession with them on the court than without them playing. The two players who played the most for their teams did so for a reason. The Atlanta and Seattle offenses were much more prolific when Elizabeth Williams and Breanna Stewart were on the floor. While a number of the league’s star players made the list, there were also a number of under the radar players who were included.
While Seattle’s offense was clearly better when Breanna Stewart was on the court, the difference on defense is more remarkable. The team was solid defensively when she was on the court, it was horrific without her there, giving up more than 20% more points per possession in the limited minutes in which she sat on the bench. Compared to the list on offense, many more bench players made this list. This may be due to inefficiency during garbage time or because bench players are on the court at the same time as opposing bench players who are not as effective on offense. Other notable players on both lists include Maya Moore, Sue Bird, Alysha Clark, and Brittney Griner.