WNBA Inside the Game powered by AWS is the new basketball intelligence platform that provides fans with a deeper layer of live stats and comprehensive analytics during games. Inside the Game offers fans a deeper understanding of the WNBA and what happens on the court. 

Check out everything you need to know about the league’s newest Inside the Game stat: Shot Difficulty. 

What is Shot Difficulty? 

Shot Difficulty measures the expected field-goal percentage, leveraging player-tracking data to unlock new insights into how the shooter and the defense interact. 

Measured as Expected Field Goal Percentage (xFG%), it is a way to quantify the baseline probability of a shot being made based on the exact context of the attempt, completely independent of whether the ball actually goes through the net. 

Shot Difficulty evaluates the environment around the player at the exact millisecond the ball leaves their fingertips. It strips away the player’s individual shooting talent and answers the question: How likely is an average player to make this exact shot under these specific conditions? 

 How does Shot Difficulty work? 

The WNBA’s tracking system uses advanced cameras to capture spatial relationships on the court at 25 frames per second. For each shot, the data spans from 1 second before the shot until the ball is released to calculate various features. The model does not account for situational features such as the shot clock, player identity, or score differential. These real-time features fuel a machine learning model trained on thousands of historical WNBA shots. 

To calculate the difficulty of any given attempt, the model instantly measures several critical variables: 

Shooter Features 

• Shot Distance: Distance from player’s center of mass to the hoop 

• Shooter’s Vertical Tilt: Degrees of the shooter’s tilt with respect to their positioning perpendicular to the court’s surface (Z axis) 

• Head Angle: Angle of the shooter’s head relative to the basket 

• Head Facing Percentage: Percentage of time the shooter’s head has potential visibility of the basket leading up to the shot 

• Speed: Shooter’s speed at the time of the shot 

• Velocity to Basket: Shooter’s velocity with respect to the direction of the basket. This is measured by how the shot distance is changing over time 

•  Rotational Speed/Velocity: Direction and speed the shooter’s hips are rotating with respect to the basket 

• Full Rotation: Total degrees of rotation the shooter rotates in the second before and after the shot 

• Hang Time: The time spent in the air from the last time the shooter leaves the floor before the release up to the release time 

• Air Time Distance: Two-dimensional distance the shooter travels after the last takeoff to release 

Defender Features 

• Closest Defender Joint Distance: Distance from the closest defender’s nearest hand and the ball 

• Relative Height of Contest: The difference between the closest defender’s nearest hand height and the height of the ball 

• Defensive Hand Contest Angle: Angle between the closest defender’s hand and the shooter’s potential apex 

• Vision Interference: The extent to which the defender is hindering the shooter’s view of the basket 

• Elbow Distance Prior To Shot: Distance between the closest defender’s nearest hand to the shooter’s elbow in the 1 second leading up to the shot 

•  Defender Hip Distance: Distance between defender’s and shooter’s hips 

• Defender Angle Relative to Basket: Angle between the closest defender and the shooter, and the shooter and the hoop \ 

• Defender Speed/Velocity: Speed and direction with which the defender is moving with respect to the shooter 

• Pressure Score: Defensive pressure exerted on the shooter by the matchup defender 

• Average Pressure Score: Average pressure exerted on the shooter by all defenders on the court 

Why does it matter? 

For decades, field goal percentage was the go-to measure of shooting prowess. But raw percentages ignore context. Shot Difficulty closes that gap, connecting the box score to the eye test. 

It’s part of the next wave of real-time stats and insights we’re bringing fans, powered by AWS AI.