Joined: 31 Dec 2004 Posts: 922 Location: Durham, NC
Posted: Thu Jul 19, 2007 11:42 am Post subject:
kjb wrote:
For example, back in 04-05, I tracked half a season of the Wizards defense. The counterpart data said that Hughes faced 18.8 FGA per 48 minutes. My tracking put it closer to 12 FGA per 48 minutes. Counterpart data said Haywood faced 11 shots per 48 minutes -- my tracking put him at 21+. These are HUGE differences, and they're very important, in my opinion.
T-Mac is being guarded by Hughes out near the perimeter. Hughes, as he is known to do, gambles and goes for the steal. McGrady drives by him into the paint where he faces Haywood and attempts a lay up.
Your tracking (I'm assuming) would assign that FGA to Haywood. Counterpart data would assign it to Hughes. In this case, I'm inclined to agree with the Counterpart Data. Why? It was Hughes' defensive assignment and he blew it.
I just want to echo what other people have said about their being overlap between the box score stats and DeanO's drtg.
That isn't necessarily a problem. If you wanted to you could have a metric which was just 2 parts drtg and 1 part +/- (which could make sense if you thought that +/- was less reliable than drtg).
Then the question becomes how do you weight box score stats differently from drtg? Put another way, what would the "stat-based" component of this rating look like without including the +/-? Who improves or suffers compared to drtg by itself.
The other question I have about +/- is whether you feel like it's "noisier" for low minute players than box score stats are. My anecdotal impressions is that for low minutes players +/- is less stable from year to year than box score stats, but I haven't looked at that systematically.
Joined: 03 Jan 2005 Posts: 689 Location: Washington, DC
Posted: Thu Jul 19, 2007 12:07 pm Post subject:
gabefarkas wrote:
kjb wrote:
For example, back in 04-05, I tracked half a season of the Wizards defense. The counterpart data said that Hughes faced 18.8 FGA per 48 minutes. My tracking put it closer to 12 FGA per 48 minutes. Counterpart data said Haywood faced 11 shots per 48 minutes -- my tracking put him at 21+. These are HUGE differences, and they're very important, in my opinion.
T-Mac is being guarded by Hughes out near the perimeter. Hughes, as he is known to do, gambles and goes for the steal. McGrady drives by him into the paint where he faces Haywood and attempts a lay up.
Your tracking (I'm assuming) would assign that FGA to Haywood. Counterpart data would assign it to Hughes. In this case, I'm inclined to agree with the Counterpart Data. Why? It was Hughes' defensive assignment and he blew it.
Actually, it would split credit/blame between Haywood and Hughes. Which (in my opinion) is more accurate than the counterpart data because it accounts for Hughes as the primary defender and Haywood's help responsibilities.
By the way, your example is interesting because if the counterpart system matched McGrady to Hughes, it would have been wrong most of the time. The way the Wizards matchup, they likely would have put Jeffries on McGrady. _________________ My blog
T-Mac is being guarded by Hughes out near the perimeter. Hughes, as he is known to do, gambles and goes for the steal. McGrady drives by him into the paint where he faces Haywood and attempts a lay up.
Your tracking (I'm assuming) would assign that FGA to Haywood. Counterpart data would assign it to Hughes. In this case, I'm inclined to agree with the Counterpart Data. Why? It was Hughes' defensive assignment and he blew it.
Your argument makes sense with this example, but what about something like this: Hughes blows an assignment, Haywood comes to help and forces an awkward layup miss. Now Hughes gets credit for Haywood's effective help defense. kjb's tracking indicates that there is help defense on a large number of plays, and therefore that counterpart data is largely affected by who the help defender is on the floor.
Or to take your example one step farther, Hughes blows the assignment, Haywood comes to help and because of that TMac dishes to an open Yao for the dunk. With counterpart data Haywood gets penalized for that dunk, but really the breakdown is Hughes' fault.
There's a lot of "cloudiness" in this manner with counterpart data. I don't know whether it is more or less cloudy than any of the other measures we have out there, but it's not nearly as cut and dried as you make it sound.
Joined: 27 Jan 2005 Posts: 523 Location: cleveland, ohio
Posted: Thu Jul 19, 2007 1:32 pm Post subject:
I just "created" a defensive stat called Defensive Composite Score
good job.... definitely a nice effort, plus the complete listing you've presented for the most part looks very good.....
I'm personally not a fan of the counterpart data because it's based on an automated matchup system. It doesn't really say how good a man defender a player actually is.
although i'm guessing alot of us (myself included) have quoted this data for just this purpose, as you stated the data simply shows that when PG A was on the floor this is what his team's opposing PGs did while he played, same for the SG, etc, and that in and of itself is incredibly valuable information, because what was once just a single team defensive FG% (or eFG%) is now broken down even further...
yes it doesn't take into consideration defensive switches, zones, or shots blocked by players other than the counterpart, but considering this information is gleaned simply from play-by-play data and not from actual video, which few of us have access to nor the time to view it if we had the access, its very useful and why i am a big fan of it...
it shows opposing nj nets SFs shooting an eFG% of just 41.5% with a very low PER of 11.0 when vince carter was at SF, insinuating carter is a lock down defender. but if you watch new jersey you know jason kidd often guards the opposing SG or SF, giving carter the easier assignment. but what it does show is that someone (or a combination of someones) is playing awfully good defense...
same for bruce bowen in san antonio. his SF counterpart stats:
these numbers show a counterpart eFG% of just 40.5% and a low PER of just 11.3. but again if you watch the spurs you know bowen (or ginobili) routinely guard the tougher SF or SG when barry's in the game, so someone was playing great D...
after viewing this data for 3-4 years now, i find it extremely valuable for rating players defensively, and when used in conjunction with +/- or adjusted +/-, patterns do emerge helping to show which players are better or worse defenders...
Denver still consistently posts better defensive numbers with Nene on the court than Camby.
the numbers you showed aren't exclusively either/or - for example in 06-07 camby played 2369 minutes, nene just 1715, and from this page:
it looks like camby and nene were on the floor together for at least 657 minutes, which is over 1/3 of nene's total playing time. both were good defenders, but if one is going to say nene is a better defender than camby in particular, then you are talking about just 1715 - 657 = 1058 total minutes of nene without camby. how significant is it to say a player playing those few minutes is a much better defender than one who played more and that in the eyes of some was one of the best defenders in the league?...
I think Camby's selection was one of the worst Award blunders ever. Yet, unlike the furor over Nash's MVPs, this is the first mention I have seen of it on this board.
the nuggets were just 11th best in the league in least points allowed per defensive team possession in 06-07, 12th best in 05-06, and actually gave up more points per team defensive possession in 06-07 compared to 05-06. the bulls went from 7th best in the league in 05-06 in least points allowed per team defensive possession, to best in the league in least points allowed per team defensive possession in 06-07, giving up 0.030 less points per defensive team possession. they improved offensively just 0.011 points per offensive team possession (23rd best in 05-06 to 19th best in 06-07)...
four bulls players - hinrich, deng, gordon, and duhon - played just over 1/2 of the team's total minutes played each season. ben wallace played about the same number of minutes as tim duncan did in 06-07 and the team improved from 41-41 to 49-33, but based solely on per game point differential, from an estimated 42-43 wins to 54 wins. but wallace got all of one first place vote for DPOY, and wasn't even named to the 1st or 2nd all-D teams...
the spurs finished 3rd in least points allowed per team defensive possession in 06-07, and bowen/duncan finished 2nd and 3rd in the DPOY voting and both were named to the all-D 1st team. go figure...
Joined: 31 Dec 2004 Posts: 922 Location: Durham, NC
Posted: Thu Jul 19, 2007 3:12 pm Post subject:
kjb wrote:
Actually, it would split credit/blame between Haywood and Hughes. Which (in my opinion) is more accurate than the counterpart data because it accounts for Hughes as the primary defender and Haywood's help responsibilities.
Hmmm, I'm not sure I necessarily agree with that either. If Haywood blocks or successfully defends the shot, then I would say he deserves all the credit, not just half of it. If Haywood is caught off guard and can only half-heartedly defend the FGA, then I might say Hughes deserves most of the blame.
kjb wrote:
By the way, your example is interesting because if the counterpart system matched McGrady to Hughes, it would have been wrong most of the time. The way the Wizards matchup, they likely would have put Jeffries on McGrady.
Eh, just a hypothetical with the first guy that came to mind...
Joined: 03 Jan 2005 Posts: 689 Location: Washington, DC
Posted: Thu Jul 19, 2007 9:17 pm Post subject:
BenF's post was pretty interesting, and actually did a better job making my point than I did.
Re: the splitting of credit/blame between Haywood and Hughes, the point Dean drummed into me is to avoid making judgements in the tracking about who I think deserves the credit/blame. Just record what happened. In the example given, Hughes allowed penetration, and Haywood helped. Whether Hughes' man scores or gets his shot blocked, the result ends up split between the two defenders. The relative values of different defensive activities shows up in analysis of the numbers.
Bob: I understand your point about how you use the counterpart data. I still think manual tracking is still the best way to understand individual contributions on the defensive end, but I concur that it is time-consuming. While it's true that counterpart data shows that someone played good defense, it often doesn't say who that someone was. _________________ My blog
How to fix the double counting: I've tinkered with adjusting DCS by either removing the box score stats I used completely, and I've also tried weighing the box score stats and defensive rating each 0.5. The latter seems to work the best. What does everyone think?
I also added in counterpart PER adjusted for position, and that was a great addition. It really helped guys like Tayshaun Prince, Bruce Bowen, and Raja Bell who were rated too low. However, it has also vaulted Manu Ginobili to the top of the rankings...
That rank order for the top 10 DPOY votegetters seems ok. Using your new formula who are the top 10 among all players in the league? How well does it sort guys into top, middle and bottom?
6 of those players weren't starters (7 if you count Ginobili). Players are getting punished for matching up against good players. If I can figure out some way to adjust for that, that would help.
It's pretty evenly distributed in terms of position throughout, with a slight skew favoring big men.
Something that I have not seen mentioned yet is where defensive systems are set up in such a way that they allow the offensive player to get past the defender, but only in a certain direction on the court (i.e. funneling). A lot of times, fans think that the defender got beat, where in fact the defender is merely funneling the opponent into the help defense. It doesn't matter if the opponent ends up making the field goal with a hand in his face, the defender has done his job.
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