Glossary

This page of our site will include act as an evergreen glossary of statistics used on BBall Index. We will make update as appropriate, and hope to expand into more comprehensive explanations/graphics/videos over time for metrics from us and elsewhere.

 

Opportunity & Usage Metrics

Ball Control

Ball Control is the percentage of a team’s time of possession (ball in a player’s hands, not being passed) that a player commands, among the time that they’re on the court.

Formula: Ball Control = (Time of Possession/Offensive Possessions) / (Seconds on Offense per Possession on Court/Offensive Possessions)

 

Minutes/Gameplay Consistency

Our consistency calculations look at game by game performance/minutes and calculate their variance. Players that have higher consistency ratings have values that are more similar to each other game to game. Higher consistency of performance can be good, but players with lower consistency and outlier higher performances also have value. For more information on the methodology and calculations, go to this link or this one.

 

Scoring Possessions

A “scoring possession” is any possession ended by a player through a shot (made or missed), turnover, or trip to the foul line.

Some examples for an Anthony Davis post up:

  • He shoots and misses – Yes, this is a scoring possession
  • He has to pass back out for a reset – No, this is not a scoring possession
  • He turns the ball over on a pass out – Yes, this is a scoring possession
  • He passes to a cutter who scores, giving him an assist – No, this is not a scoring possession

 

Team Minutes/Possession/Touch/etc. Share

These calculations look at the percentage of the team’s minutes/possessions/touches/etc. that an individual player commands. If a player has a 5% minute share, their minutes make up 5% of their team’s total minutes played.

Formula: Value Share = Player’s Value / Team Total Value

 

Time of Possession

Time of Possession is the length of time a player has the ball in their hands. At the team level, we use this data to calculate how long the ball is in a player’s hands vs in the air for passes.

Formula: Time of Possession = Touches * Time per Touch

 

Total Offensive Load

Total Offensive Load is an estimate of how much a player directly contributes to an individual possession through their shooting, creating, passing, and turning the ball over (while attempting to shoot, create, or pass).

Offensive load was designed by Ben Taylor (@ElGee35). For more information on methodology, click here.

Formula: Offensive Load = (Assists – (0.38 * Box Creation)) * 0.75) + FGA + FTA * 0.44 + Box Creation + Turnovers

 

True Usage

True Usage is an estimate of usage that incorporates tracking data to better measure the true usage a player has of the team’s offense. This is done by incorporating potential assists.

True Usage was designed by Seth Partnow (@SethPartnow). For more information on methodology, click here.

 

Contextual Data

Lineup Talent, and associated measures

Lineup Talent/Defensive Talent/Playmaking/etc. are estimates of the environment a player plays within based on the lineups they’re used in. These will not be uniform for players on the same team. Our current published talent grades are assigned for each player in every lineup, with averages of the four players playing alongside the player in question being averaged for that lineup’s rating. Lineup ratings are then averaged, weighted by minutes played, to calculate the final average lineup rating.

 

Lineup Spacing

Lineup Spacing is an estimate of the degree to which the offensive players’ willingness and ability to shoot from the perimeter forces defenders to defend the 3-point line, thus creating space for drives/cuts/etc. This is the only contextual lineup stat that looks at all five players in a lineup to calculate the rating, rather than just the four players alongside the player in question. 3-point shooting frequency and accuracy are both accounted for to calculate a rating for each lineup, which are then averaged, weighted by minutes played, to calculate the final average lineup spacing rating.

 

Matchup Difficulty

Matchup Difficulty is an estimate of the difficulty a defender takes on with their defensive matchups/assignments. We develop matchup difficulty using partial possession player tracking data, to capture switches, help defense, etc., which allows us to capture how much time a player spends defending each opposing defender (rather than 1 player per possession calculations you may find elsewhere).

Calculations look at the usage tier of players defended to derive a final difficulty value. Players are rewarded in this rating more for defending top caliber players, and that benefit decreases in a tiered fashion as players defend lower tier opponents.

Future versions of this metric will further differentiate for time guarding All-Star caliber players, as well as an adjustment to better account for team schemes.

 

D Position/Role Versatility – Versatility Defending Offensive Positions/Offensive Roles

Versatility Defending Offensive Positions/Roles captures a player’s versatility through the lens of defending players of differing offensive positions or offensive roles. The metric looks only at actual time spend defending those roles, not performance by those offensive players in those situations.

We develop this versatility metric using partial possession player tracking data, to capture switches, help defense, etc. which allows us to capture how much time a player spends defending each opposing defender (rather than 1 player per possession calculations you may find elsewhere). From this, we can infer that the team’s coaching staff trusts the player to defend a wider range of offensive talents.

A player defending a wider array of positions/roles will have a higher value for their versatility, whereas players guarding fewer positions or roles will see lower versatility ratings.

Future versions of this metric will include an adjustment to better account for team schemes.

 

Performance Consistency

Please refer to Minutes/Gameplay Consistency metric writeup above.

 

Pace Impact Estimate

Pace Impact Estimate estimates the degree to which a player’s court presence impacts the pace of play for their team, through looking at on/off-court impacts as well as stats correlating to pace increases and decreases. For example, committing or causing turnovers correlates to increased pace.

Pace Impact Estimate was originally calculated by 538. You can read more about their methodology here.

 

Perimeter Shooting

Openness Rating

Openness Rating estimates the degree to which a player is open on their 3-point attempts. Input data comes from NBA.com, and buckets players’ 3-point shots in four bins of how close the closest defender was at the time the player took their shot (0-2 feet, 2-4, 4-6, 6+ feet).

League average percentages are calculated for each range, and the value of a shot in each area is based on the value over the baseline 0-2 feet tightly contested shots, enabling proper valuation of the four categories. From there, the player’s average openness value is calculated.

 

3-Point Ratios

C&S : PU Ratio: ratio of Catch & Shoot 3-point attempts to Pull Up 3-point attempts

C3 : ATB Ratio: ratio of Corner 3-point attempts to Above the Break 3-point attempts

 

3-Point Gravity

Gravity data looks at player frequency/volume and efficiency to estimate the degree to which their shooting ability from that part of the floor will influence defenses to cover them more closely. Negative values are good, and the higher the value, the more we’d expect a defense to respect that player’s scoring from that area. Additionally, for 3-pointers, shots from further out past the 3-point line are rewarded more than 3-pointers right at the line.

Having high 3-point gravity and demanding more defensive attention should open up cutting, post ups, and driving lanes. Having high rim gravity should help collapse the defense on cuts, post ups, or drives to open up outside shooting opportunities.

BBall Index’s Andrew Patton first developed the gravity calculations in 2019, and did his methodology writeup here.

For full NBA, WNBA, and NCAA gravity data and 3D charts, go here.

 

3PT Foul Rate

3-point foul rate captures the percentage of 3-point attempts a player draws a foul on.

Formula: 3PT Foul Rate = (3-shot Fouls + 3PT & 1 fouls) / (3PA + 3PT & 1 fouls)

 

3PTA Rate

3-point attempt rate is the percentage of a player’s shots taken that are from 3-point distance.

Formula: 3PTA Rate = 3PA / FGA

 

One on One

Total Isolations

Totals isolations capture a player’s scoring possession volume in one on one situations on both the perimeter and interior.

Formula: Total Isolations = Perimeter Isolation Scoring Possessions + Post Up Isolation Scoring Possessions

 

Total Isolation Impact

Total Isolation Impact seeks to capture the points a player adds above/below what an average player would score if given the same volume of possessions in similar situations.

The next update of this metric will include stabilized values for players with volumes below the calculated thresholds based off of their offensive role. For example, if a player is 15 possessions below the threshold and is a Pick & Pop Big, their data will be infused with 15 average efficiency possessions for Pick & Pop Bigs in that play type, then reduced down to the original possession volume.

Formula: Total Isolation Impact = Total Isolation Points – ((Perimeter Isolation Possessions * League Average Perimeter Isolation Efficiency) + (Post Up Possessions * League Average Post Up Efficiency))

 

Isolation Foul Drawn Rate

Isolation Foul Drawn Rate captures the percentage of isolation scoring possessions a player draws a shooting foul.

Formula: Isolation Foul Drawn Rate = Shooting Fouls Drawn during Isolation Possessions / Total Isolation Possessions

 

Off-Ball Movement

Movement Attack Rate

Movement Attack Rate measures the percentage of a player’s first chance half court scoring possessions they spend in one of our two movement categories, either cutting to the rim (no dump offs) or in an off-screen action.

Formula: (Off Screen Possessions + (Cutting Possessions – Dump Offs)) / (Half Court Possessions – (Miscellaneous Possessions + Putbacks))

 

Movement Distance Rating

Movement Distance Rating seeks to answer: “does the player cover a lot of ground for the offensive role they’re in?” It’s calculated as offensive feet traveled per minute played, with a role adjustment to adjust for the types of actions a player spends their time in and show distance traveled relative to other players in the same offensive role.

 

Movement Speed Rating

Movement Speed Rating is role adjusted average offensive speed, which captures how fast a player moved relative to other players in their offensive role.

 

Movement Points

Movement Points are all points from cuts (no dump offs) and off-screen scoring possessions.

 

Movement Impact

Movement Impact seeks to capture the points a player adds above/below what an average player would score if given the same volume of possessions in similar situations.

The next update of this metric will include stabilized values for players with volumes below the calculated thresholds based off of their offensive role. For example, if a player is 15 possessions below the threshold and is a Pick & Pop Big, their data will be infused with 15 average efficiency possessions for Pick & Pop Bigs in that play type, then reduced down to the original possession volume.

Formula: Movement Impact = Total Movement Points – ((Non-Dump Off Cutting Possessions * League Average Non-Dump Off Cutting Efficiency) + (Off Screen Possessions * League Average Off Screen Efficiency))

 

Finishing

Adjusted Drives

Adjusted Drives per 75 offensive possessions on court is just that, with a regression of league average driving rate possessions to stabilize small samples.

 

Drive Passout Rate

Drive Passout Rate is the percentage of drives a player passes to a teammate, rather than attempting to score.

 

Drive Assist Rate

Drive Assist Rate is the percentage of drives a player passes to a teammate and is credited with an assist

 

Drive Foul Drawn Rate

Drive Foul Drawn Rate is the percentage of drives a player draws a shooting foul during their drive.

 

Contact Finish Rate

Contact Finish Rate is the percentage of shooting fouls a player converts on. Without other data to measure contact, shooting fouls are proxied in to estimate that aspect of the game.

 

Adjusted FG% at Rim

Adjusted FG% at the Rim shows FG% at the rim, with small samples adjusted downward by a Sigmoid function.

 

FGM at Rim vs Expectations

FGM at Rim vs Expectations seeks to capture how well a player scores at the rim on the attempts they have once there, and doing so while capturing and adjusting for variables that may impact performance finishing at the rim (such as spacing, and if they were creating their own shot or not).

To calculate this metric, we take into account factors such as floor spacing (see explanation in context data section), player physical tools (height and weight), and the percentage of shots at the rim that were assisted, to estimate the shots at the rim a player would be expected to have made based on those factors. That expected value is then compared with the actual value, to determine the residual (this stat).

 

Playmaking

Role Adjusted Assist Points

Role adjusted Assist Points per 75 offensive possessions on court shows assist point performance relative to expectation based on others in the same role. This metric seeks to answer: “Are they a good passer for their role?”

We like to use this to help identify players in non-traditional playmaking roles that are good ball movers, as well as separate the true playmakers from the rest among players within roles that will accrue assist volumes just based on what the players are asked to do.

 

Passing Aggressiveness

Passing Aggressiveness is the percentage of passes a player has that are a bad pass turnover, which we proxy as aggressiveness. Lower bad pass turnover percentages indicate a player is making safer passes and is more of a ball mover than a playmaker.

Other metrics within the playmaking category use this metric to help identify if a player is a good playmaker for their level of aggressiveness. That isn’t done here with this measure alone.

Formula: Passing Aggressiveness = Bad Pass Turnovers / Passes

 

High Value Assists

High Value Assists, which we may also refer to as Morey Assists, are 3-point assists, rim assists, and free throw assists.

 

Box Creation

Box Creation is an estimate of open shots carved out for teammates by drawing defensive attention using box score metrics only.

Calculations developed by Ben Taylor (@ElGee35). You can read more about his methodology here.

 

High Value Assists +/-

High Value Assists +/- assesses a player’s ability to generate high value scoring opportunities for teammates relative to their passing aggressiveness and ball control. This methodology looks to evaluate two key areas.

  1. Are players efficiently making use of the time they have the ball to create?
    1. Players creating high value opportunities for teammates without having the ball in their hands often can more easily be identified this way.
    2. Similarly, it can help identify players that are generating assists in a Rondo Assist fashion where they possess the ball for long periods of time and eventually pass to someone who takes a shot.
  2. Is the volume of high value scoring opportunities good based on how aggressive the player is with their passing?
    1. There is a strong positive relationship between passing aggressiveness (measured via Bad Pass Turnover %) and high value assist rates. The regression we use helps identify players who are creating more than we’d expect based off of their aggressiveness going after those tough passes.
    2. Likewise, on the opposite end it can tell us if a player is underperforming from a high value assist standpoint based on their aggressiveness and if they’re just not good at threading needles.

This metric, along with Role Adjusted Assist Points / 75 Possessions and Passing Aggressiveness, can help us identify each player’s passing style and proficiency within that style.

 

Roll Gravity

Team Roll Man Share

Please refer to the Minutes Share notes in the Opportunity & Usage section of the glossary.

 

Roll/Pop/Slip/Total Roll Man Impact

Please refer to the Isolation Impact or Movement Impact notes in the One on One and Off-Ball Movement sections of the glossary.

 

Screen Assists

Screen Assists capture screens that free up players for a score, crediting the screener with a screen assist.

If you’d like to learn more, ask Jazz Twitter and they’ll tell you all about them.

 

Rim Gravity

Please refer to the Gravity notes in the Perimeter Shooting section of the glossary.

 

Roll Gravity

Post Style Rating

Post Style Rating evaluates a player’s post style in terms of the types of shots they take (jumpers, to rim, hook shots, up and under, or post pin) in terms of degree of difficulty, based on league average efficiencies.

A player with a high Post Style Rating is attempting easier shots in the post, whereas a player with a lower rating has a style geared toward lower efficiency shots.

 

Post Up Draw Foul Rate

Post Up Draw Foul Rate shows the percentage of a player’s post scoring possessions they draw a shooting foul.

 

Post Up Impact

Please refer to the Isolation Impact or Movement Impact notes in the One on One and Off-Ball Movement sections of the glossary.

 

Potential Assists per Post Pass

Potential Assists per Post Pass capture facilitation ability of big men from the post through measuring how often their pass outs directly lead to a shot attempt by a teammate.

 

Roll Gravity

OReb/DReb Chance

OReb/DReb Chances per 75 possessions on court capture how frequently a player has an opportunity to obtain a rebound, based on their position relative to where the ball was rebounded.

 

Adjusted OReb/DReb Success Rate

Adjusted OReb/DReb Success Rate is a Second Spectrum stat capturing success rate on attempted rebounds, adjusted to exclude times the player deferred a rebound to a teammate.

 

OReb/DReb Positioning

OReb/DReb Positioning shows the average feet away from the rim a player was when they captured their rebounds. We can use this to tell how players are generally positioned on the court. Being closer to the rim will yield a higher percentile and letter grade.

From this, we can tell that Bigs with higher values (and thus lower percentiles) are being utilized more on the perimeter than others. The inverse is true for guards grabbing their rebounds closer to the rim.

 

Real Adjusted OReb/DReb Rate

Real Adjusted Rates use ridge regressions to capture the impact a player has on their team’s performance in a specific area based on their presence on-court.

This, along with Adjusted Reb Success Rates and Adjusted Box Out Rates, can help tell us what kind of rebounder a player is, and how much they help their team based on their role and performance within that role.

Source data is calculated at NBAShotCharts and can be found here.

 

Putback Impact

Please refer to the Isolation Impact or Movement Impact notes in the One on One and Off-Ball Movement sections of the glossary.

 

Adjusted Box Out Rate

Adjusted Box Out Rate is an estimate of defensive box outs per shot from the opposing team while a player is on court, with small samples regressed average box out rates by defensive role.

 

DReb Success vs Expectations

DReb Success vs Expectations evaluates the difference between what we’d expect a player’s success rate to be, based on their physical profile and situational factors, with their actual success rate on rebounds.

Expected rates are based off of the player’s height, weight, lineup box out tendencies, player defensive positioning, and contested DReb%.

 

Matchup Data

All matchup data leverages partial possession player tracking data, which captures which offensive player each defender was defending for each portion of each defensive possession.

This better captures real defensive assignments and switches, help defense, etc. than saying that each defensive player defended one offensive player each possession.

 

Perimeter Defense

Real Adjusted Turnover Rate

Please refer to the Real Adjusted OReb/DReb Rate notes in the Offensive/Defensive Rebounding glossary section.

 

Loose Ball Recovery Rate

Loose Ball Recovery Rate seeks to capture a player’s ability to recover loose balls. Since we’ll only have data on specific participants in loose ball situations, those must be relied upon for this calculation.

Loose balls recovered is simple enough via tracking data, but participation in those situations is based off of loose ball fouls (tried, but collected a foul instead), lost ball turnovers off of steals (had the ball taken from you), and loose balls recovered (succeeded). If a player attempted to recover a loose ball but didn’t initially lose it, eventually get it, or commit a foul along the way, it won’t be tracked here.

Formula: Loose Ball Recovery Rate = Loose Balls recovered / (Loose Ball Fouls + Lost Ball Turnovers Off Steals + Loose Balls Recovered).

This metric was originally calculated by BBall Index’s Krishna Narsu. His initial writeup can be found here.

 

Passing Lane Defense

Passing Lane Defense captures how disruptive players are through their ability to intercept passes and deflect the ball. Passing Lane Defense is a rate stat, showing impact per 75 possessions on the court defensively.

Formula: Passing Lane Defense = Deflections / 75 Possessions + Interceptions / 75 Possessions

 

Matchup Adjusted Defensive Feet / Minute

Matchup Adjusted Defensive Feet per minute captures how far a player travels defensively for someone defending the players they defend. Using matchup tracking data and capturing the percentage of time a defender spends defending players in each offensive role, we can estimate how far they would be expected to travel and compare that with their actual travel distance.

 

Shot Profile Deterrence

Shot Profile Deterrence, or Q-RAD, is a defensive statistic that attempt to measure how a player deters the offense from taking high efficiency shots. Made or missed shots do not matter in this context, only attempts. This metric captures how offensive players’ shot profiles change when guarded by specific defenders, with value added through those profiles changing away from high efficiency areas for those specific players (the rim and corner 3s come to mind) and into lower efficiency areas (such as the mid range).

On its own, Q-RAD is not a measure of defensive quality. It is best to interpret as a player’s style in impacting the opposing offense, and digested along with other defensive stats and defensive impact stats for a full defensive evaluation.

Q-RAD was developed by BBall Index’s Andrew Patton. Andrew’s methodology and writeup on Q-RAD is found here.

 

Hunted in Perimeter Isolation

Our Hunted in Perimeter Isolation metric looks at how frequently opposing offenses attack players in perimeter isolations as a result of switches, with a defensive role adjustment to help account for the fact that a big man is more likely to be attacked in these situations than a shooting guard.

The role adjusted result shows who, with their role being considered, is seen by opposing defenses as a viable target. It also shows who defenses are less apt to attack in those situations.

Future iterations of this metric will further integrate defensive scheme estimates to help adjust players up/down that are where they are due to more or less switchiness in team defensive scheme.

 

Lineup Interior Defense

Please refer to the Lineup Talent notes in the Context Data portion of the glossary.

 

Interior Defense

Rim Deterrence

Rim Deterrence is a role adjusted measure of how a player’s presence on-court impacts opponents’ frequency of attacking the rim, captured by Andrew Patton’s Regularized Adjusted Deterrence metric (RAD). You can read more about Andrew’s methodology here.

We care about this stat for Bigs, not Guards or nearly as much for Wings.

 

% Rim Shots Contested

This is the percentage of shots at the rim while the player is on the court defensively that they contest.

 

Block Rate on Contests

Block Rate on Contests shows a player’s success rate of blocking shots on the ones they contest.

 

Rim dFG% vs Expected

Rim dFG% vs Expected is the FG% players shoot on shots at the rim above/below what Second Spectrum would expect based on shot locations. Low samples are regressed with league average percentages.

This does not adjust for the shooting ability at the rim of specific players faced.

 

Adjusted Rim Points Saved / 36 Minutes

Adjusted Rim Points Saved / 36 Minutes is a measure of points “saved” on shots at the rim by the defender based off of their ability to contest shots, with smaller samples regressed with league and role average rim dFG% values.

This concept was first developed by Seth Partnow, and a writeup on the methodology and math behind the metric can be found here or  here.

 

Lineup Perimeter Defense

Please refer to the Lineup Talent notes in the Context Data portion of the glossary.