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Defensive plus/minus

 
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Eli W



Joined: 01 Feb 2005
Posts: 287

PostPosted: Fri Feb 25, 2005 6:29 pm    Post subject: Defensive plus/minus Reply with quote

http://maverickblog.blogspot.com/2005/02/defensive-stat.html

Quote:
One of the statistics I have been looking at a lot lately has been the on court off court defensive stats at the 82 games site. Many believe figuring out who are good defenders and who are not is almost impossible. I think its difficult, but not impossible. I believe the following on court off court defensive statistic is one of the best barrometers I have found to giving a fairly accurate account as to who can play defense and who can't. What the following stat shows is who gave up more points against the other team when they were on the court as compared to their own teamates when they were off the court. I have calculated the top 100 or so players in the NBA plus anyone who recieved more then two votes in the ALL NBA defensive team voting in any of the last 3 seasons. I think its a complete list of the best players and defenders. The list is for the last 3 years starting with 3 years ago and finishing with their average for the last 3 seasons combined.
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nate33



Joined: 04 Feb 2005
Posts: 2

PostPosted: Fri Feb 25, 2005 7:30 pm    Post subject: Reply with quote

Are those the "top 100 or so" best defensive players, or the top 100 players? How are the top 100 defined?

The reason I ask is that I noted the glaring omission of Brendan Haywood. The Wizards have allowed 8.1 fewer points per 100 possessions with Haywood on the floor this year. Last year, it was 5.5 points fewer. The year before, 2.9 fewer. Surely he ranks higher than the likes of Peja Stojakovic and Carmelo Anthony. I guess he didn't make it past whatever filter you used to weed out certain players.
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Minstrel



Joined: 24 Jan 2005
Posts: 1
Location: California, USA

PostPosted: Fri Feb 25, 2005 9:50 pm    Post subject: Reply with quote

Quote:
I believe the following on court off court defensive statistic is one of the best barrometers I have found to giving a fairly accurate account as to who can play defense and who can't.


What are you comparing it to, to determine accuracy? That is, what's your measure of accuracy?

Is it just who you expect to see in such a list?
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Eli W



Joined: 01 Feb 2005
Posts: 287

PostPosted: Sat Feb 26, 2005 11:51 am    Post subject: Reply with quote

Sorry if it wasn't clear, but I'm not the author of that article. I just found it interesting so I posted the link to it.
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kjb



Joined: 03 Jan 2005
Posts: 671
Location: Washington, DC

PostPosted: Sun Feb 27, 2005 9:30 am    Post subject: Reply with quote

Maybe someone can fill in the blanks on his method. What is he calculating?
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KD



Joined: 30 Jan 2005
Posts: 143

PostPosted: Sun Feb 27, 2005 4:10 pm    Post subject: Reply with quote

I was about to rip the author's equation for having Reggie Miller make the top 20, but then I remebered Miller getting a solid defensive PER in the last Forecast. Looking it up, (3.69), Hollinger attributes his ranking to playing alongside and switching matchups with Ron Artest. Obviously, this hasn't been the case this season, as they've yet to play a game together.

How do most you regard Miller's defensive prowess?
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Kevin Pelton
Site Admin


Joined: 30 Dec 2004
Posts: 680
Location: Seattle

PostPosted: Sun Feb 27, 2005 5:41 pm    Post subject: Reply with quote

He's averaging the defensive on-court/off-court difference over the last three years per 82games.com. It's more of an organization of that data than a new way to rate things. ...
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kjb



Joined: 03 Jan 2005
Posts: 671
Location: Washington, DC

PostPosted: Mon Feb 28, 2005 7:53 am    Post subject: Reply with quote

Tracking this over 3 seasons makes this kinda interesting, but there needs to be some other kind of control here when it comes to identifying individual defensive achievement. Using the player pair data might be a good start. An example from this season's Wizards:

The Wizards are 3.4 pts per 100 possessions better defensively when Jamison is on the court. Wow -- Jamison must be a decent defender, right? Well, not really. Through 2/15, Jamison had played 59% of his minutes with Brendan Haywood -- and the team is 8.7 pts per 100 possessions better when Haywood is on the court. The player pair data reveals that the team gives up 7.6 pts per 48 minutes MORE when Jamison is on the court without Haywood.

Basically, I think this list is kinda interesting, but I think the method needs some work to make it worthwhile.

By the way: I don't think this is worth a new thread, but I've been tracking Wizards individual defense the past 20+ games. Against the Wizards, the Bulls shot 35-86 for the game. They were 0-13 on shots Haywood contested. The 0-13 vs. Haywood lowered the Bulls FG% from .479 (what they shot vs. all the other Wizards combined) to .407.

(I'll now duck the roundhouse headslap coming from North Carolina for my use of fg% instead of efg. Sorry, Dan, I haven't had a chance to do the calculations.)

Bonus factoid: The Wizards gave up 27 open or wide open shots vs. the Bulls. Chicago made 18 of them, including 7 3s.
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Keven



Joined: 28 Feb 2005
Posts: 1

PostPosted: Mon Feb 28, 2005 10:49 pm    Post subject: Reply with quote

Thanks for checking out my site. The stat looks at the top 100 overall players in the NBA[I used my Ball Theory list] plus any player that recieved more then 2 votes for the all defensive team in any of the last 3 seasons. That added another 7 players[Grant, Snow etc.]. So I feel the list is a comprehensive list of the top NBA players and top NBA defenders. Haywood may be an under rated defender[I like him], but he didn't get the all defensive votes and he came up short on my Ball Theory top 100. I didn't do every player in the NBA because when you get to players with small minutes the numbers get eratic. So it was more an idea of who can play defense among the best players in the NBA then who was the best defenders. So the Haywoods and Watsons of the world got left out.

The list was not a new stat, but just a 3 year look at the on court off court defensive numbers from 82games. There is no doubt there are weaknesses in the stat. Who you play with. Who replaces you ussually in the lineup. Tempo. Stat aberations like Reggie Millers from 2 seasons ago when he had a great number, but it was in very few games so likely very misleading. Etc, etc, etc. However, its just another defensive stat to look at and I felt many of the kinks of the stat got ironed out over a 3 year look. Maybe not all though.

Thanks again.
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kjb



Joined: 03 Jan 2005
Posts: 671
Location: Washington, DC

PostPosted: Tue Mar 01, 2005 4:59 am    Post subject: Reply with quote

Keven: I think the effort was worthwhile -- I think it can be improved by finding a way to incorporate other data (such as player pair info).

By the way: I think we've reached "...Kev..." saturation in basketball sabermetrics. If another one comes in, we may have to send him to hockey.
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