Basketball Possessions Analysis:
- by Prof. Roberto Azar - July 26, 2012
When using possessions to rate offenses and defenses, an excellent
exercise in getting to know basketball , the benefits of this definition becomes clear.
We'll Analyze the following 2 situations: 1) A player brings the ball up court, takes a 20 foot jump shot and makes it. 2) A player brings the ball upcourt, takes a 20 foot jump shot and misses, but a teammate rebounds, misses the putback, then get his own rebound and finally puts in a layup.
The first situation involves one scoring possession and one total possession regardless of which definition is used.
The second situation has one scoring and one total possession using the first definition.
Using the other meaning, the second situation involves one scoring possession and three total possessions.
Now, which situation represented the better offense ?
About the Concept:
Definition of Possession: the time your team gets the ball, all the way
up until the other team gets it back.
At least for the purpose of this number, offensive rebounds dont add possessions. This is comprehensible, since to determine the cost of a turnover, for instance, we want to know what the total chance there was that youd score some points before the other team got the ball back. That includes getting offensive rebounds, since the turnover eliminates the possibility of getting second chance points just as it did first chance points.
About the Formula:
The total number of possessions a team has can be calculated as
Field Goals Made + Opponent Def. Rebounds + Turnovers +
Up to the Line for 2/3 free-throws series)
Meanwhile another formulas use the coefficient "FTA / 2" or "FTA*0.4", etc., the eBA System uses the exact number of possession ended "up to the line" for 2 or 3 throws.
This formula, with the "up to the line" coefficient, was basically created because we felt it was a better evaluation of offensive and defensive efficiency than to count stats like total rebounds, or total points scored or allowed or divide the free throws attempts by estimates number of "2" or multiply by "0.4".
About the rebounds formulas, you hear talk about "win the rebound war, win the game" what is in general true, but not always. The addition of the 3 point shot to the game of Basketball causes to re-estimate the value the formula as well. If in short a team has the opportunity to score at least 3 points on every possession, instead of two, so we have added an additional variable into the equation.
An additional way of thoughts is that by using FGA as a loss of possession, a possession is lost every time a ball is shot. As a result a new possession starts with an offensive rebound. This works against a good offensive rebounding team because it punishes their Points / Possession evaluation.
To resume this question, as said above, from the moment there is discrepancy between the number of free throws attempted per game so that the FTA/2 or FTA*0.4 is not always an evaluation according to the rules, since on any given night the number of 1, 2, or 3 free throw attempts for each fouled possession will vary. The eBA System uses the exact number of possession ended "up to the line" for 2 or 3 throws as a better measure regardless of the total number of attempts.
Consequently many coaches are now using what is called Points/Possession, or Turnovers/Possession. The Points/Possessions is an impartial reliable stat when all things are considered.
However it doesn't take into account the optimal pace as which a team plays. Team A that receives 90 points may actually produce a better defensive efficiency than team B that allowed 80 points: in a fast paced game, Team A received 90 points but in 90 possessions.
This means their defensive efficiency was 1.0. Team B on the other hand received only 80 points but in a much slower paced game in 60 total possessions. That is a defensive efficiency of 1.3 actually worse than team A who allowed ninety points.
Points per possession is a completely good stat but what is more important is to break it down into ranges such as an offensive or defensive efficiency when you score or allow 90-100 points, 80-90, 70-80 and so forth.
The parameter we will find is that the team have better offensive and defensive efficiency ratings when he plays
at its team's optimal pace. The eBA System do this break down in his "Quarters Reports", when the game is Analyzed every 5 minutes by separate.
From Another Point of View:
Possession Evaluation (PE)
Is a method of rating a team's performance in three areas of the game: offense, defense, and rebounding.
The formula was developed by Dean Smith and detailed in his book Basketball ~ Multiple Offense and Defense.
PE begins by counting each team's total possessions during the game.
Offensive efficiency is represented by points per possessions (pts/poss or ppp).
Defensive effectiveness is the opponent's pts/poss. A superior team should exceed .85 points per possession on offense and keep the opponents below .75 ppp.
"Percent Loss of Ball" (% LoB) is the percentage of possessions that end before a shot (FG or FT) is attempted. This is basically just a way to correct for the overall pace of the game when considering turnovers. %LoB can be used to indicate a team's own ball-handling skills, as well as the effectiveness of their pressure defense. A %LoB of .13 is excellent; .15 to .18 is good. You want to force you opponent into the .22 range.
The differential in the teams' total possessions is an indicator of rebounding. Coach Smith considers a FG attempt as an end to the team's possession; the ball is no longer in their control. If the shot misses, a possession is literally up-for-grabs. The better rebounding team should have more possessions by the end of the game.
Total Possessions are calculated by counting the three events which end a possession:
- FG attempts. While the ball is in the air neither team controls it. A rebound of a missed shot (even an offensive-rebound) begins another possession.
- FT opportunities. This counts the entire series of FTA, not each FTA separately. This is referred at the eBA System as the "Up-to-the-Line" opportunities. When all the FT have been shot, the ball is given to the other team. With the only exceptions are technical fouls or intentional fouls, but these are relatively infrequent. Only 'stand-alone' opportunities are counted here: when a player goes to the line for the double-bonus, or when a player is fouled on a missed shot (which means officially no FG attempt). FT attempts following a made basket are not counted, as they are really part of the same possession that produced the shot. The FG ended that particular possession.
About 'Points Created':
( 'Points Created' is a trademark of Bellotti Basketball ).
Bob Bellotti has a different formula for arriving at possessions.
It differs in that he counts the stats which begin a possession: opponent's FG, opponent's turnovers, and rebounds. Instead of trips to the foul line, his system counts opponent's free-throws (divided by 2). It also includes a team's blocks (also divided by 2). It was designed for the NBA game (which has no 1+1), and it is not well suited for the college game.
It comprises all current primary and secondary statistical categories:
points, rebounds, assists, steals, blocked shots, missed shots (both field goals and free throws), turnovers, and personal fouls. Essentially, Points Created adds the good things a player does and subtracts the bad things.
Points Created =
PTS + AST * (2-VBP) + (REB + STL + BLK) * VBP -
(FG Miss + FT Miss + TOV) * VBP - 0.5 * VBP * PF
You can divide by minutes or games. VBP is the value of a ball possession, as he estimates apparently on a seasonal basis (perhaps on a team-season basis) as
VBP = (Ball possessions)_LeaG/PTS_LeaG
Ball possessions = REB + FGM + TOV + FTM/2 + BLK/2
The ever-fluctuating Value of Ball Possession (VBP) makes Points Created work. The VBP is the leagues average points per possession. Last year, NBA teams scored an average of 90.6 points per 100 possessions, making the VBP .906.
Based on the VBP, each category is assigned a value. For example, because a ball possession was worth .906 last year, each reboundwhich is the act of gaining possession of the ballwas .906 points. A turnover has the opposite effect; it is the loss of a possession and therefore, was worth the negative value of ball possession, -.906 last season.
When each category is weighted and a players stats are calculated, a single number
resultsthe points a player creates through his overall play, a bottom-line stat that reveals his value.
Points Created is valuable in many ways. It is comprehensive, and can be used to evaluate players and teams on any level of Basketball, in any league where statistics are kept. You can use it to study one game, many games, a season, and a career.
It also is useful in far-ranging areas. With Points Created, you can compare players who have been traded, rate prospective draft choices, identify underrated players who are about to bloom, and compare teams against each other.
Finally and most important, Points Created is accurate. It measures overall performance rather than a single skill (such as shooting) or set of skills (such as shooting, rebounding, and shot-blocking). Therefore, the result is a clear composite of a team or player's total performance.
This contention is borne out by facts. For example, the NBA's MVP has ranked in the top 4 in Points Created in 23 of the past 24 years.
Points Created can be likened to a baseball batting average, except that a good Basketball "batting average" is .450 and above. The following list will help you interpret the PC ratings.
Superstar category. Normally, only a handful of players each season reach this level of performance.
All-Stars are in this range, or either just below or above it.
Good players who are sometimes outstanding fall into this category.
Regulars. Solid players who are either starters or among a team's first seven or eight regulars.
Poor. Players in this category are frequently rookies, or veterans whose skills are declining.
Awful. Players in this category are living life on the edge. Most are soon traded or released.
The Bellotti Basketball System has two advantages: first, it can be calculated from boxscores or season-ending stats. When this system is applied, one needn't laboriously count trips to the foul line; second, as it was stated above, Bellotti has
developed a formula which, using the team's points per possession, can evaluate players' overall value to the team.
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