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Re: Usage and efficiency stats
Posted: Thu Feb 06, 2014 7:24 pm
by Mike G
It is an enduring mystery why ORtg and DRtg are still considered to be equally good approximations of what they purport to measure. They aren't. Full stop. ORtg is pretty good, whereas DRtg is really quite terrible...
I agree with all of this. See the OP. ORtg is almost meaningless without Usg%. It's also not very meaningful without DRtg.
DRtg alone doesn't tell us much without ORtg and Usg. Just as there's not much information in just a person's height, or just his weight, or just his fat content. Together, they tell us something.
Given that we can concoct a combination that in fact seems to concur with a player's known best season, maybe we are on to something.
If you aren't playing much D, or are part of a team that doesn't play much D, what does that say about your offensive stats? That they aren't translatable to a more competitive environment?
Yet if you have at your disposal something like DRtg -- basically your team's DRtg plus or minus a quantity that depends on your blocks and steals -- then you have something better than league ORtg to compare to your ORtg -- it's the avg league ORtg of the games in which you were actually playing.
DRtg doesn't have to be an "equally good approximation" to still be better than nothing.
How great is an ORtg of 113 with TS% of .565? Orlando Woolridge did this while scoring 26 pts/36 in 1991.
His 7.1 Reb/36 was above average in the league; but his Reb% of 9.3 was below avg. That's what happens when your team is out-rebounded by 3 per game.
His DRtg of 116 was just a bit worse than his team's 114.7
Re: Usage and efficiency stats
Posted: Thu Feb 06, 2014 7:28 pm
by schtevie
Y'know, upon a moment's more of reflection, it occurs to me that I shouldn't have been so down on DRtg relative to ORtg. At least with the former, the overall range of estimates approximates what +/- data reveal reality to be (the point of proper apportionment of credit, for the box score statistical void, still applying).
The same simply cannot be said for ORtg, where the range of estimates (as revealed by these most excellent player seasons) significantly exceeds even that suggested by APM.
Given these facts, why should a metric with a built in offensive bias (i.e. USG%), reinforced by more offensive bias (ORtg^2), and rendered somewhat imprecise (1/DRtg^2) be relied upon to indicate overall player greatness?
Re: Usage and efficiency stats
Posted: Thu Feb 06, 2014 10:29 pm
by Mike G
I don't know that I'd call Usg% a 'bias' for offense, when it simply distinguishes those who are more active on offense.
It's not a bias 'against defense'; it's neutral.
DRtg is largely the team DRtg.
It looks as if the proper exponent is 2.5
Re: Usage and efficiency stats
Posted: Fri Feb 07, 2014 1:00 am
by schtevie
But, of course, it is a biased measure. Consider the extreme hypothetical: a ham-handed defensive supah-genius, having the ability to prevent any and all from scoring in the paint, but who on offense would turn the ball over every time the ball was touched, were he given such an opportunity. Such a player would (hypothetically) be the greatest of all time, but would have a (rational) USG% of zero. Next, relax the assumption, but think of truly great defensive specialists. They are completely ill-served by this metric.
Re: Usage and efficiency stats
Posted: Fri Feb 07, 2014 1:25 pm
by Mike G
Sigh, 'tis true. Ben Wallace had 10.5 Usg% -- and 10% is about as low as any major player goes -- along with O/D of 117/93 at best.
Thinking of an adjusted Usage% = (20+Usg)/2
This acknowledges that 1/2 of a player's presence is on defense, gives that an avg value of 20.
With that and a 2.5 exponent on O/D, Ben registers a 27.2 -- still below all those high Users.
Re: Usage and efficiency stats
Posted: Mon Apr 07, 2014 5:29 pm
by Mike G
Another thread inspired me to take up this topic again.
A formula to approximate WS/48 when knowing just ORtg, DRtg, and Usg% is:
altWS/48 = (Usg+40)*(ORtg/DRtg)^(3.33)/334 - .087
This version does not seem to produce such extremely bad/weak WS/48 rates.
b-r.com lists 48 players with >100 min this year and negative WS/48. Their avg is -.046
altWS gives the same 48 players an avg of -.016; 12 are above zero.
Kobe has WS/48 of
-.096 this year; in the alt version, he's
-.006
Yet league WS add up to the same total. They've just been redistributed.
Here are the top 20 players in minutes played, comparing the 2:
Code: Select all
. Player WS/48 alt Player WS/48 alt
Carmelo Anthony .169 .158 LeBron James .265 .264
Kevin Durant .306 .307 Josh Smith .021 .043
DeMar DeRozan .142 .144 Klay Thompson .113 .112
Monta Ellis .078 .082 Stephen Curry .219 .207
Nicolas Batum .127 .116 Kyle Lowry .193 .182
Paul George .181 .196 Lance Stephenson .130 .122
John Wall .129 .129 Wesley Matthews .140 .138
Damian Lillard .158 .147 Chandler Parsons .129 .126
DeAndre Jordan .188 .237 Jeff Green .056 .066
Blake Griffin .205 .202 Joakim Noah .191 .198
Not much difference for most players. Most are within the rounding error you get from lack of a decimal place in b-r.com's ORtg and DRtg.
Re: Usage and efficiency stats
Posted: Mon Apr 07, 2014 5:56 pm
by Mike G
Last year's Finals summaries can be seen here --
http://www.basketball-reference.com/pla ... inals.html
They show ORtg and DRtg but not WS or WS/48. By the formula above, we get:
Code: Select all
Miami Heat Min TS% Usg% ORtg DRtg w/48 W
LeBron James 301 .529 29.7 113 105 .179 1.11
Chris Bosh 240 .491 18.5 108 104 .112 .55
Shane Battier 87 .689 15.4 141 110 .292 .52
Dwyane Wade 255 .505 28.5 104 108 .094 .49
Mike Miller 152 .841 7.7 131 112 .154 .48
Ray Allen 193 .715 15.2 121 116 .103 .41
Chris Andersen 71 .714 13.6 118 103 .165 .24
Joel Anthony 15 .500 6.8 146 117 .206 .06
Udonis Haslem 64 .477 8.1 102 114 .012 .02
James Jones 12 .600 25.0 96 121 .003 .00
Rashard Lewis 12 .333 33.0 65 125 -.062 -.02
Mario Chalmers 221 .509 19.7 87 112 -.010 -.05
Norris Cole 82 .328 16.8 75 115 -.046 -.08
. total 3.74
. Spurs Min TS% Usg% ORtg DRtg w/48 W
Kawhi Leonard 255 .583 17.5 120 103 .199 1.04
Tim Duncan 254 .554 25.2 112 104 .163 .85
Danny Green 248 .649 15.8 115 108 .119 .61
Tony Parker 246 .472 25.4 103 113 .057 .29
Manu Ginobili 199 .560 22.4 101 112 .045 .19
Boris Diaw 94 .615 12.4 116 116 .070 .13
Nando De Colo 5 .0 0 226 118 .956 .10
Gary Neal 171 .552 18.6 100 115 .023 .08
Matt Bonner 36 .506 14.0 111 106 .101 .08
DeJuan Blair 17 .446 32.6 95 95 .130 .05
Tiago Splitter 107 .509 18.7 91 107 .015 .03
Tracy McGrady 14 .000 9.5 98 103 .039 .01
Patrick Mills 13 .400 17.3 93 115 -.002 .00
Cory Joseph 43 .473 18.0 85 106 -.004 .00
. total 3.45
The total Wins add to 7.19
De Colo had a DReb and an Ast in 5 minutes (no shots); throw out his garbage time, and we're closer.
Leonard also leads the Spurs in WS/48 for this season.