USER GUIDE FOR REAL TEAM RATINGS REPORTS
UPDATED AS OF MAY 5 2009
The only update done on May 5 was a new standardization adjustment for the wins and losses against playoff teams factor, which is described in detail in the appropriate section below.
The Real Team Ratings(RTR)are intended to rate teams with respect to how much success they are most likely to have in the playoffs. They are not intended to be simply a summary of how well teams have done. The ratings are calculated for all teams, even though 14 of the 30 NBA teams do not qualify for the playoffs. Even though they will not be playing any playoff games, the ratings for the lower teams nevertheless give an accurate measure of how well those teams would most likely do if they were in the playoffs. So for those lottery teams, RTR is an interesting hypothetical.
As of 2009 the RTR rating system was improved. It was improved to make absolutely certain that you can predict the outcome of the playoffs in advance as accurately as possible. All crucial factors are now included and weighted very carefully. The biggest and most important improvement for 2009 and beyond was the introduction of points for wins over and points subtracted for losses to the top 16 teams (which would be the playoff teams themselves.)
Broadly speaking, the system is a combination of net efficiency (net points per 100 possessions), net points per game, the defensive overweight adjustment, the wins and losses against playoff bound teams, and the relatively small pace overweight adjustment. Each of these is now described in detail.
THE FIVE FACTORS USED FOR REAL TEAM RATINGS
1.NET EFFICIENCY
Offensive Efficiency minus Defensive Efficiency equals Net Efficiency. A weight of 2.0 is applied to Net Efficiency.
1a. Offensive Efficiency: Points Scored per 100 Possessions
1b. Defensive Efficiency: Points Allowed per 100 Possessions
Note that net efficiency, or net points gained or lossed per each 100 possessions, is double weighted, whereas the simple net points per game is single weighted. In the original version of the Real Team Ratings, the efficiency was single weighted and the points per game was not a part of the system.
2.NET POINTS PER GAME
Points Per Game Scored Minus Points Per Game Allowed. A weight of 1.0 is applied to Net Points Per Game. In other words, the straight up points scored per game minus points allowed per game is input into the formula.
3.DEFENSIVE OVERWEIGHT ADJUSTMENT
The teams are sorted by defensive efficiency. Then, using a range from 5.8 to -5.8, points are assigned, in equal increments of .4, to each team in order of how it ranks according to defensive efficiency. Specifically, the team with the best defensive efficiency (fewest points allowed per 100 possessions) is given 5.8 points, the 2nd most defensively efficient team gets 5.4 points, the third most defensively efficient team gets 5.0 points, and so on, until the least defensively efficient team gets minus 5.8 points.
It is well known that, for the playoffs, how well a team can defend is generally somewhat more important than during the regular season. This factor answers the need to overweight defending in order to get accurate playoff projections. The adjustment gives an increase or a decrease in every team's rating in accordance with how each team ranks in defensive efficiency in the NBA.
The amount of the adjustment is carefully calibrated to be sufficient without being excessive. Since almost all teams ramp up their defense in the playoffs, you have to be careful here to avoid getting carried away and putting in adjustments that are too large.
4.WINS OVER AND LOSSES TO PLAYOFF TEAMS
Each team's win-loss record is accessed for games it played against the top 16 teams and, separately, each team's win-loss record is accessed for games it played against the top 10 teams. These two records are added together, which has the effect of double weighting wins and losses versus top 10 teams, while leaving wins and losses versus the 11th through the 16th best teams single weighted. In other words, the sum of the wins versus the top 10 teams is added to the sum of the wins versus the top 16 teams, and the sum of these two sums is added to the overall Real Team Rating formula (with weight of simply 1.0). Losses in games against the top 10 and against the top 16 are subtracted from the overall Real Team Rating in the same way that the wins are added.
In late April 2009, it was realized that since the teams play a different total number of games against the top 10 and the top 16, that a distortion would be introduced into the RTR as designed at the time. Therefore, a new adjustment of the wins/losses against playoff teams was rolled out. The purpose of the adjustment is to standardize the wins/losses against playoff teams records so that the differing number of such games played by different teams is no longer a distorting factor.
Were this adjustment not done, the impact of wins and losses against playoff teams on the overall RTR would be greater for teams that played more games against other playoff teams, which is a significant distortion.
The adjustment works as follows. Whichever team played the most games versus top 10 and top 16 teams (combined) is ascertained, and then that number of games is used as the standarization base. The unadjusted wins percentage for each team is then multiplied by the standardization base to yield the best estimate for how many wins each team would have won against the top 10 and the top 16 had they played as many games (the standard number of games) as the team that played the most such games.
The best estimate for standarized losses is then of course the number of standard games minus the standardized wins. Both the standardized wins and the standardized losses are projected to two decimal points (two numbers beyond the decimal points.)
This factor, wins over and losses to playoff teams, is the key improvement from the early versions of RTR, and helps to clearly establish Real Team Ratings as the most accurate playoff predictor possible. By counting in the overall formula actual wins and losses in games between the likely playoff teams, you have gone in a straight line directly to evidence for the question we are out to answer: how good are the teams really going to be in the playoffs, according to everything known now?
5.PACE OVERWEIGHT ADJUSTMENT
The teams are sorted by pace. Pace for each team is the average number of possessions per game for that team's games. Then, using a range from 2.9 to -2.9, points are assigned, in equal increments of .2, to each team in order of how it ranks according to pace. Specifically, the team with the slowest pace (fewest possessions per game) is given 2.9 points, the 2nd slowest pace team gets 2.7 points, the third slowest pace team gets 2.5 points, and so on, until the fastest pace team gets minus 2.9 points.
The reason for the pace adjustment is that there is a mild but definite correlation between slower pace and winning playoff series. It is a little more difficult, on average, for fast pace teams to win playoff series than it is for slow pace teams to win them. Therefore, a small adjustment called the pace overweight adjustment is factored in to RTR.
Why exactly do slower paced teams have a slightly easier job winning playoff series? Consider an example. For example, consider the Denver Nuggets. They are one of the fastest paced teams in the NBA during the regular season. If you just look at the efficiency measures, the Nuggets might appear to be almost identical to another, much slower team. But these two teams would be very different when you look at efficiency and pace together. In theory, slower paced teams can more reliably reproduce their nice regular season net efficiency in the playoffs than can faster paced teams, mostly because the playoffs feature a higher defensive intensity and aggressiveness, which automatically slows down the pace.
Suppose that in the playoffs, the fast paced Nuggets and a slow paced team play. Each team had almost exactly the same offensive, defensive, and net efficiency numbers during the regular season. By playing extra hard on defense, the slow pace team can automatically slow down the game to some degree, which will disrupt the offensive (and possibly the defensive) efficiency of the Nuggets, the team that was fast pace in the regular season. In other words, there will be fewer possessions for the fast pace team in the playoff games than it typically had in the regular season. This in turn means that the fast pace team will be disrupted from what they did during the regular season to one extent or another.
This means that for the fast pace team, both the offensive and the defensive efficiency could change in the playoffs from what it was in the regular season, due to all of the changes forced on the fast pace team by the change of pace. Both the offensive and the defensive efficiency might change, and each change could be either for the better or for the worse, but by far the most likely changes would be that the offense would be substantially less efficient, while the defense would not be changed much. A much less efficient offense, but about the same defense, is exactly what we have seen from the Nuggets in their numerous playoff series losses in recent years.
In extreme cases, such as the fastest pace team being slowed down dramatically in the playoffs by an extremely slow team, the pace adjustment may be inadequate, so that there may still be some forecast error even after everything we have done.
The bottom line is that in all known cases, faster paced teams do not do as well in the playoffs as they do in the regular season, all other things equal. If a fast paced team wants to win in the playoffs, it would be wise to do some things better in the playoffs than they did those things in the regular season, in order to compensate for being forced to operate at a slower pace.
CALCULATION OF RTR: THE FORMULA
The easiest way to describe the final calculation of RTR is to give you the formula.
RTR = 2 X Net Efficiency + Net Points per Game + Defense Overweight Adjustment + Number of Wins Over Top 10 Teams + Number of Wins Over Top 16 Teams - Number of Losses To Top 10 Teams - Number of Losses To Top 16 Teams + Pace Overweight Adjustment
OTHER FACTORS THAT COULD SWING A SERIES ARE UNKNOWABLE
To get even better accuracy than RTR, you would have to know what the injury situation is going to be in late April and throughout May and June. And you would have to start guessing how unmeasurable factors such as currently unknown coaching strategies and possible injury problems will affect individual playoff series.
IT IS NOT SAFE TO USE THE RTR TO TRY TO WIN MONEY BETTING ON GAMES OR SERIES
As of 2009 you can no longer use the actual ratings as a starting point for estimations of final score margins of games between teams, which is no real loss, because you could not do that very accurately with the previous system anyway. Remember, you should never bet money on the outcome of games or even on the outcome of playoff series, because there are always variables that neither you nor anyone else will be aware of that will go into determining the outcome of each game.
ADJUSTING BASE RTR FOR FACTORS NOT INCLUDED IN BASE RTR THAT CAN BE MAJOR FOR DETERMINING WHO WINS PLAYOFF SERIES
Of all the popular American sports Leagues, the NBA is the one where the better team is most likely to avoid being upset in the playoffs. Therefore, the RTR system can be used to gain knowledge of which team is most likely to win playoff series. It can also be used to determine whether how good various players played led to an upset or not, and to get a general idea of how much better or worse than expected teams played in playoff series.
In order to do these things, however, it is necessary to modify base RTR for at least two factors that can not be directly embedded in it: home court advantage and players unavailable or playing badly due to injuries.
Even just to start with, due to a small amount of unavoidable statistical error remaining in the base RTR, there has to be a 7-12 points difference between teams before you can start to have any big confidence that one team will defeat another in the playoffs. More importantly, there are also factors unknown until close to or exactly when the series is actually being played, especially what the injury situation for each team is.
Another factor that becomes a big one when two teams with very similar ratings are playing is home court advantage. Home court advantage is estimated to be worth between 5 and 7 points.
Even if it were not for the injury wild card factor, use of RTR to predict playoff series prior to March 1 would not be very useful, due to the need for a fairly high percentage of the season to be over before the projections in base RTR are statistically meaningful, and due to the fact that the ratings are not relative to time, but rather expand with time.
MAJOR FACTORS DETERMINING WHO WINS PLAYOFF SERIES NOT BUILT IN TO THE BASIC RTR
1.HOME COURT ADVANTAGE
The home court advantage in RTR terms is believed to be 5 to 7 points
2. PLAYERS UNAVAILABLE (OR PLAYING POORLY) DUE TO INJURES
The impact relative to RTR is believed to be mathematically anything from almost 0 to 100 points for each injured and unavailable player who played during the regular season, depending mostly on how good the injured player is and depending on to what extent other players are able to step up and replace the injured player or players. Although the mathematical range of impact is 0 to 100, the realistically true and common relevant range covering the loss of starters and key reserves, is about 10 to 60 RTR points.
Players who were injured the entire season are irrelevant, except of course they are relevant in the hypothetical sense of how the season could have been different. Players who were injured relatively early in the regular season, in November or December, are only slightly relevant, and the loss of them would be a much smaller number of reduced RTR points than when the loss is later. Players who were injured late in the season, from mid-February to mid-April, have the most relevancy to whether playoff series can be won or lost, and the RTR reduction for them is much higher.
INJURY ADJUSTMENT TO RTR DIFFERENTIALS (DEVELOPMENTAL BUT HAS PASSED INITAL REVIEWS)
This adjustment is under development and review. However, it has passed initial approvals, which means it is very likely to be officially adopted in the near future.
The base or starting point is the quality of the player, as shown by the Real Player Ratings including the defending adjustment.
BASE FOR THE DOWNWARD ADJUSTMENT TO RTR DUE TO INJURY/UNAVAILABLILTY OF PLAYERS
Almost Perfect Player: 125
Historical Superstar: 113
Superstar: 98
Star: 81
Outstanding/Solid Starter: 64
Major Role Player: 49
Role Player: 36
Minor Role Player: 25
Very Minor Role Player: 16
Poor Player: 9
Very Poor Player: 4
Extremely Poor Player: 1
Remember, the base is just the hypothetical maximum possible impact, and is not a relevant real world outlook by itself. The RTR impact and the real world impact of the loss is determined by many variables, the most important of which are when the player was lost, and to what extent the other players can make up for the loss of that player.
DOWNWARD ADJUSTMENT FACTORS TO THE RTR INJURY ADJUSTMENT BASE
FACTOR FOR TIME IN THE SEASON WHEN THE PLAYER WAS LOST
November .1
December .25
January .45
February .70
March .95
April 1.0
FACTOR FOR TO WHAT EXTENT OTHER PLAYERS CAN MAKE UP FOR THE UNAVAILABLE PLAYER
We currently have to describe this adjustment generically:
(1)The player or players getting the lost minutes are close in quality (no more than one Real Player Rating category lower) and also close in terms of basketball position played, to the lost player: .4 to .6
(2)The player or players getting the lost minutes are close in quality, but are not close in terms of the position(s) played: .55 to .75
(3)The player or players getting the lost minutes are not close in quality, but are close in terms of the position played: .7 to .9
FACTOR FOR IMPORTANCE OF PLAYER TO THE TEAM (SHOWN BY MINUTES PER GAME)
32 mpg and more: 1.0
28 to 31.1: .9
24 to 27.9: .8
20 to 23.9: .7
16 to 19.9: .6
12 to 15.9: .5
8 to 11.9: .4
4 to 7.9: .3
Less than 4: .2
AN EXAMPLE OF HOW BASE RTR IS ADJUSTED FOR INJURIES: THE 2009 BOSTON CELTICS
Ok, now lets consider an example to see how all of this works. We have this year Kevin Garnett, one of the very best players in the NBA, not available to the Celtics due to injury. Garnett is in the almost perfect player range, so you start with 125 points as the unadjusted impact of the Garnett loss to the Celtics' Real Team Rating.
Now we need to breakdown that 125 gross number. First, we need the when the player was lost factor. Although Garnett came back for a few games in March, he was essentially lost for the season in February, so the factor to use is .70.
Next we need the stepping up of other players factor. Rajon Rondo has responded by being even better than he was in the regular season, which already was at the superstar level. And Rondo overall is playing as good as Garnett would be if he were playing, at the almost perfect level to be exact. So this turn of events would put the Celtics in the (2) situation above, so the factor to use would be between .55 to .75. Based on how extremely well Rondo is playing, and based on the overall resiliency of the Celtics, we will use .60 as the factor.
The third and final factor to use on the gross injury base RTR adjustment is how important the player is to the team, as shown by minutes per game. Garnett was about 31 minutes a game this season, so the factor to use is .9.
Now we can calculate by how many points we should downgrade the Celtics' RTR due to the loss of Kevin Garnett:
125 *.60 *.70 *.90 = 47.3
LEON POWE
Now we need to figure out how much the Celtics have lost due to Leon Powe not being available. Because the Celtics are also without Leon Powe, a very underrated 17 minutes a game forward, whose 2008-09 quality level was major role player.
Since he is a major role player, we start with 49 points. He was lost at the very end of the season, so the when lost factor is 1.0. Due to the simultaneous loss of Garnett and Powe, the Celtics are severly depleted upfront, which means you can positionally replace Garnett but not both Garnett and Powe at the same time, which in turn translates into a factor of about .75 for the to what extent other players can replace Powe factor. Finally, Powe played about 17 minutes a game this season, which means you should use a factor of .6 for importance of the player to the team.
Now we can calculate about how many RTR points the Celtics have lost due to Leon Powe not being available:
49 * 1.0 * .75 * .60 = 22.1
The two losses cost the Celtics roughly 47.3 + 22.1 = 69.4 points.
The Celtics' 2008-09 RTR unadjusted for injuries was 54.4. The Chicago Bulls' RTR was -24.02. So the difference between the two teams started out as 78.42. But the loss of Garnett and Powe cost the Celtics roughly 69.4 RTR points, leaving them with only a measly 9 points advantage over the Bulls, or 15 points once you add on the 6 points for home court advantage.
According to the Guidelines for Interpreting Differences in Real Team Ratings (which is reprinted from the overall User Guide below) a 15 points difference means there was somewhere between a 72% and an 80% that the Celtics were going to win the series.
So in real life, the series played out exactly as the RTR predicted that it would, at least once you have adjusted the RTR for players not available!
So what has to be done to figure out the real differences between any two playoff teams is to start with RTR, and then use the under development but destined to become officially approved Injury Adjustments. So we will have RTR-IA to use to predict playoff series, and to judge whether a series has been an upset or not, and also to judge just how heroic players such as Rajon Rondo are. (Note: always remember to add in about 6 points for the home court advantage, too.)
Bottom line for the Celtics: Rajon Rondo has been out there making up for both Kevin Garnett and Leon Powe. He has been a hero, not only for that, but also because he was already a superstar in the regular season, and then he had to get even better than being a superstar.
How would you like someone to come up to you and say to you: "You are a superstar, but that is not good enouogh right now. Now you have to be better than a superstar, you have to be almost perfect." You might be thinking to yourself: "Yeah right, I'm going to be able to suddenly be even better than I already am. I'll try, but I doubt it's going to happen; I'm not a miracle worker".
Whereas Rondo said: "No problem, I'm down with that." And then he proceeded to go out there and be almost perfect, as if that is as easy as waking up in the morning.
So Rajon Rondo is no doubt one of the heroes of the 2009 playoffs. And he has a very good chance of being the first ever Real Playoffs MVP here at Quest, which will be an honor given out to the player who did the most to help his team, regardless of exactly how many games and series the team won.
It's a good thing he already has a ring, because if he didn't fully earn it last year, he sure as hell earned one this year.
But the Celtics will need a miracle to defeat the Magic despite this.
GUIDE TO INTERPRETATION OF DIFFERENCES BETWEEN TEAMS' REAL TEAM RATINGS
In the numeric interpretaton guide that follows, the word "roughly" is repeatedly used in front of the probability numbers, as a reminder about the small amount of unavoidable statistical error, and to emphasize that unknown factors, especially injuries, will in some cases result in substantially different actual probabilities.
The probability percentages are based on the historical results in the NBA:
REMEMBER:
In order to realistically compare teams using RTR, particularly if your objective is to know who is most likely to win playoff series, you MUST add 5 to 7 points to the RTR of the team that has home court advantage (HCA), and you MUST use the Injury Adjustment (IA) for all injured players on all teams evaluated. The injury adjustment is under development, is in beta currently, and is described extensively above. In other words, for any and all teams being evaluated, you MUST use RTR + HCA + IA
The following guidelines assume that the HCA and all injury adjustments have been correctly done.
DIFFERENCE IN RATINGS IS BETWEEN 0 AND 5.9
The series is a complete toss-up, when statistical error is considered. There is a strong possibility of a 7 game series. The higher team has a 50% to 57% chance of winning, depending on what exactly the difference is. These probabilities are too low for anyone to have any confidence in using adjusted RTR to say who will win. All series of this type are decided quite simply by who plays better, by who coaches better, or both.
DIFFERENCE IN RATINGS IS BETWEEN 6.0 AND 11.9
The series can easily go either way, although the higher team has a slight edge, and has between a 57% to 66% chance of winning, depending on where in the range the difference is. There is a very substantial chance of a 7-game series. If the lower team wins, it is nothing more than a very minor upset. Either slight differences in the quality of coaching, certain players playing a little better or a little worse than they did in the regular season, or both, could be responsible for an upset at this level.
DIFFERENCE IN RATINGS IS BETWEEN 12.0 AND 17.9
The series can go either way, and this type of difference gives a substantial chance for a 7-game series. But the higher team has a clear edge. The higher team has between a 66% and a 76% probability of winning, depending on where in the range the difference is. If the lower team wins, it is an upset, though just a small upset. Either slight differences in the quality of coaching, certain players playing a little better or a little worse than they did in the regular season, or both, could be responsible for an upset at this level.
DIFFERENCE IN RATINGS IS BETWEEN 18.0 AND 23.9
The higher team has roughly between a 76% to 84% probability of winning, depending on where in the range the difference is. There is still a chance, but a relatively small one, for a 7-game series. If the lower team wins, it is clearly an upset, though generally not a major upset. Either coaches, certain players, or both could be responsible for an upset at this level.
DIFFERENCE IN RATINGS IS BETWEEN 24.0 AND 29.9
The higher team has roughly between an 84% to a 91% probability of winning, depending on where in the range the difference is. In this kind of series, often the only way the lower team can win the series is by extending the series out to 7 games and then somehow winning the 7th game, thus taking the series 4 games to 3. However, it is not uncommon, assuming there is an upset in this type of series, for the lower team to so severly disrupt the favored team that the lower team upsets the higher, favored team 4 games to 2. Whichever way it does it, if the lower team does win coming in down by this amount, it should be considered a major upset. In many such cases, the coaching would have to be very wrong and/or negligent.
DIFFERENCE IN RATINGS IS BETWEEN 30.0 AND 35.9
The higher team has roughly between a 91% and a 95.5% probability of winning. depending on where in the range the difference is. In this kind of series, often the only way the lower team can win the series is by taking the series 7 games and winning the 7th game, thus taking the series 4 games to 3. However, there have been a tiny number of series where a team with this amount of a RTR deficit has won the series by so severly disrupting the favored team that it is able to win the series 4 games to 2. In the vast majority of such cases, the coaching for the higher team was severely wrong and/or negligent. Whether accomplished in 6 games or 7, the lower team winning despite being this far behind in RTR is extremely rare, and would be considered a very shocking, historical upset.
DIFFERENCE IN RATINGS IS BETWEEN 36.0 AND 41.9
The higher team has roughly between a 95.5% and a 98% probability of winning, depending on where in the range the difference is. Obviously, an upset would be extremely rare, shocking, and historical. It would in most cases be caused substantially by incompetent and/or severely negligent coaching. With this amount of difference, any upset would almost certainly have to be with the series going all seven games.
DIFFERENCE IN RATINGS IS 42.0 AND 47.9
The higher team has a roughly between a 98% and a 99.5% probability of winning the series. Obviously, an upset would be extremely rare, shocking, and historical. It would in most cases be caused substantially by incompetent and/or severely negligent coaching. With this amount of difference, any upset would almost certainly have to be with the series going all seven games.
DEFFERENCE IN RATINGS IS 48.0 OR MORE
It is close to a 100% certainty that the higher team will win the series. Obviously, an upset would be extremely rare, shocking, and historical. It would in the vast majority of cases be caused substantially by incompetent and/or severely negligent coaching. With this amount of difference, any upset would almost certainly have to be with the series going all seven games.
