As "average allowed rebounds" should be corrected by the pos. adjustment.
The approach that the best rebounders are the most of the time also the best defenders, is an old approach that I've been quoting long time ago, and is the same that Jason wanted to approach. That bigs and inside players (the best rebounders) are also who confronts more FGA and more stops (60% of FGA are taken inside) although perimeter defenders have the distance advantage, not to mention the help that insiders produce.
The overrating is not in the possession value of rebounds against shot defense, is like assimpkisns said, rebounding is treated without the "missed".
And in the scoring logic is where is a "lot of fabric to be cut".
Joined: 30 Apr 2006 Posts: 223 Location: Pleasanton, CA
Posted: Wed Jan 09, 2008 10:29 pm Post subject:
magicmerl wrote:
asimpkins, isn't 'average rebounding' corrected for by the 'position adjustment'?
I may be mistaken, but I believe that is used to try to correct between players of two different positions, to try to cover up for that fact that rebounding so dominates WoW. But that aside, you still have a problem.
Let's look at simplified WoW rating that just focuses on shooting and rebounding:
PTS - FGA + REB
So we have two centers. Center A never shoots but he's an average rebounder and gets 10 rebounds a game. Center B never rebounds but he's an average scorer and gets 10 points a game on 10 shots (50%).
Center A = 0 - 0 + 10 = 10
Center B = 10 - 10 + 0 = 0
So Center A is valued at '10' for being an average rebounder (and a terrible scorer). Center B is valued at '0' for being an average scorer (and a terrible rebounder).
These two primary basketball skills aren't being judged the same way because you are never penalized for "missing" a rebound that you should have gotten. With rebounding, the only way to go is up. Whereas with shooting you gain or lose in comparison to how you perform against average.
The effect of this double standard is to minimize scoring to a footnote in the WoW rating. And once you squeeze out scoring, what is left? Mostly just rebounding. So whether you value it at 0.3 or 0.7 or 1.0, it doesn't make much of a difference because it makes up most of what is being measured anyway.
Last edited by asimpkins on Wed Jan 09, 2008 10:39 pm; edited 1 time in total
I suspect Berri understand very well the point, and knows he got trapped in that elemental mistake, but I don't understand his shelling strategy and how that benefit his books and his reliability in the basketball market.
He's putting himself into a shell, trying to show he's totally self convinced he's right, rather than recognize he forgot something in the building process of the metric.
And it should remain clear that WP is my favorite metric. I just fell in love with the idea of a team defense adjust as a counterparting, to make up for non existed boxscore stats (less noise than PER counterparting and +/-). I can't understand how the smartness behind that idea just forgot the zero sum approach in a piece of the game.
Joined: 26 Mar 2007 Posts: 54 Location: Orlando, FL
Posted: Thu Jan 10, 2008 10:25 am Post subject:
Quote:
So we have two centers. Center A never shoots but he's an average rebounder and gets 10 rebounds a game. Center B never rebounds but he's an average scorer and gets 10 points a game on 10 shots (50%).
Center A = 0 - 0 + 10 = 10
Center B = 10 - 10 + 0 = 0
So Center A is valued at '10' for being an average rebounder (and a terrible scorer). Center B is valued at '0' for being an average scorer (and a terrible rebounder).
Joined: 30 Apr 2006 Posts: 223 Location: Pleasanton, CA
Posted: Thu Jan 10, 2008 12:27 pm Post subject:
Thanks. I'm just blatantly repeating and summarizing what I've absorbed from much smarter WoW critics than myself.
When I saw Berri's latest comments it occurred to me this would be the best angle of attack, and not the exaggerated full possession credit for defensive rebounds nor the absence of any measure for usage (which are probably related). Those are both issues that I believe are very real and relevant as well, but the WoW crowd seems to dodge them easily.
After all they only play a small part in WinScore. The fact that they play such a small part is the biggest problem, and the one that we should probably focus on.
Joined: 03 Jan 2005 Posts: 715 Location: Washington, DC
Posted: Thu Jan 10, 2008 1:00 pm Post subject:
A point Dr. Berri has made is that the position adjustment essentially does put rebounding (and every other stat) against the league average for that position. I'm still not sure about the position adjustment, though. On one hand, it makes sense. Teams look for different statistical production from different positions, so it makes sense to compare like players to like players.
On the other hand, if a rebound adds X number of wins and a turnover costs Y number of wins, does it really matter which position produced that stat? The team effect is the same. Which makes me think that the position adjustment may, in some senses, be hiding information. The preponderance of big men at the top of non-position adjusted rankings might be an indicator of something we already know -- good big men are extremely valuable.
I also made a long point about valuation of rebounds on the WoW blog. To summarize -- WP will usually overvalue defensive rebounds because most of the credit for the defensive stop goes to the guy who collected the rebound (some credit goes to his teammates in the team defensive adjustment). This is almost certainly because there is no stat for players doing "other" defensive work such as non-block forced misses or non-steal forced turnovers. If such a stat existed, I suspect WP would look different.
As things stand now, there's no individual stat available for the most important defensive activity -- forcing misses. _________________ My blog
While the discussion of how to allocate credit for a rebound/def stop raises interesting issues, I think it misses the central point. We're not trying -- or shouldn't be trying -- to allocate credit for all rebounds. We're trying to credit players only for rebounds they add to (or subtract from) the team total. WP assumes that each rebound above position average equals an additional rebound for the team. This is the critical assumption, though never stated explicitly (that I recall), and certainly not backed with evidence.
But it simply isn't true. Garnett in his prime averaged +330 boards compared to average, but his team was just average (and Minn's rebounding has improved with his departure). Rodman in his prime was +540 reb/season, but his teams were only about +170 in those years. Berri constantly criticizes Curry for being a poor rebounder (among other things), but as a team the Knicks have been above-average on rebounds with Curry. These are just anecdotes, of course, but the pattern is quite clear: the benefit/cost to the team of a high/low individual reb total is only a small fraction of that player's total.
Someone still permitted to post over at WOW should make this challenge to Dave and Jason: stop telling us that players' reb total correlates with their own rebound total the next year (duh), and show us a connection to their team's rebound advantage. Give us examples of a team replacing a 12 Reb48 player with a 15 Reb48 player and gaining 3 boards (or gaining 3 defensive stops). Or find 10 great rebounders whose team rebound advantage was as large as that player's own advantage over the position average (over several seasons). All that requires is to find some great rebounders whose teammates were (collectively) average rebounders. If rebound opportunities are only minimally impacted by one's teammates, as WOW assumes, this should be easy.
If you take the top 10 HR hitters in baseball last year and look at their teams' HR totals, you'll find that every single team was above average in HRs, and averaged 197 HRs vs. a league average of 165. HRs are a teammate-independent stat: if I replace an average 3Bman with A-Rod, my team will hit more HRs. Rebounds are a different animal: if I look at the top 10 players in Reb48, their teams average -0.7 net reb/game (i.e. they are below average). It's clear that teams allocate rebound opportunities much more to some players than others. This is hidden from view, because we can't measure opportunties at the player level. I don't know what the true ratio of player rebounds to net team rebounds, but it's much closer to zero than to one. Thus far, Berri has made no effort to figure it out, and shows no signs of even understanding why this is an important question.
Last edited by Guy on Thu Jan 10, 2008 3:30 pm; edited 1 time in total
It's clear that teams allocate rebound opportunities much more to some players than others. This is hidden from view, because we can't measure opportunties at the player level. I don't know what the true ratio of player rebounds to net team rebounds
I think 82games track that. Rebounding skills exist, but the floor position, the height (jump, wingspan) are the main correlated things. There are secondary things related to floor position, as the bound of the ball, and secondary things related to skills, as timing and own boxing out job. A Center can have a RebR% three times better than a PG, but the opponent Center could also have the same proportion, and in the end you need to penalize every player with their around 30% of allowed off. rebounds (on average), and the same operation at the off. end.
The better rebounders in totals, like scoring, will be allways the better rebounders in totals, but an average should be 0 rating (10-3 at the defensive end, and 3-10 at the offensive end), not a total of 10. Zero sum, Guy, zero sum. But, the skills (the rebounding creation), with the exception of the J.Kidds of the world, depends more on the ball than the player.
WP assumes that each rebound above position average equals an additional rebound for the team. This is the critical assumption, though never stated explicitly (that I recall), and certainly not backed with evidence.
But it simply isn't true. Garnett in his prime averaged +330 boards compared to average, but his team was just average (and Minn's rebounding has improved with his departure). Rodman in his prime was +540 reb/season, but his teams were only about +170 in those years. Berri constantly criticizes Curry for being a poor rebounder (among other things), but as a team the Knicks have been above-average on rebounds with Curry. These are just anecdotes, of course, but the pattern is quite clear: the benefit/cost to the team of a high/low individual reb total is only a small fraction of that player's total.
<snip>
stop telling us that players' reb total correlates with their own rebound total the next year (duh), and show us a connection to their team's rebound advantage. Give us examples of a team replacing a 12 Reb48 player with a 15 Reb48 player and gaining 3 boards (or gaining 3 defensive stops).
Or find 10 great rebounders whose team rebound advantage was as large as that player's own advantage over the position average (over several seasons). All that requires is to find some great rebounders whose teammates were (collectively) average rebounders. If rebound opportunities are only minimally impacted by one's teammates, as WOW assumes, this should be easy.
This is probably the key contention, said much better than I could have said it myself.
The opportunities at the team level, like play time and possessions, are finite, no matter the distribution of those opportunities among players; but the player's opportunities could be (in an imagined extreme situation) the same as team's. That is, player's opportunities are limited by team' opportunities and teammates's opportunities. A player doesn't make a team win (at the individual game) because he scores 30, or rebounds 15 with extra opportunities, if he's neither making up teammates's opportunities, nor avoiding wasting his own opportunities at the same time.
People like to use the 2001'Iverson example with that, he uses a lot of teammates'scoring opportunities, and teammates use his rebouding and stop opportunities, if they can keep the team above average doing that extra job, they win.
And yes players waste opportunities and loose games, Garnett could be winning the game for his team, and his teammates loosing it, while Rodman's teammates no, but team or players total rebounds are irrelevant, rebounding margin is what matters. But given you gain extra points-prize scoring, then scoring action has a w% of about 40%, while rebounding action just a 20%.
"Give us examples of a team replacing a 12 Reb48 player with a 15 Reb48 player and gaining 3 boards (or gaining 3 defensive stops)."
Here are some names that could be checked to see if their cases when they moved from one team to another in recent past offer the conditions sought and what the results were:
Ben Wallace, Dampier, Chandler, Garnett, Camby, Boozer, Jefferson, Murphy, B Grant, Magliore, Shaq.
Tracking who they replaced (or the reverse who replaced them) might be clearer (less disputed) in some cases than others.
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