I have been pouring too much time into basketball research recently, but there have been some side benefits. I have developed two metrics which I will explain briefly, that measure a player's defensive contributions. These are not perfectly original, however I believe that no such metrics have been developed before.
Incidentally, look for me in an upcoming Aaron's Baseball Blog discussing more basketball-related stuff.
Individual Defensive Value
The first is called Individual Defensive Value (IDV). IDV is simply the total point value of the defensive events that a player is responsible for... his blocked shots, steals, defensive rebounds, and his personal fouls.
How do you determine the point value of a defensive event? For these formulae, I am indebted to John Hollinger and his terrific book Pro Basketball Prospectus. A less modest man than John would have called his book The Hidden Game of Basketball, because his work has had at least that much impact in terms of revolutionizing the study of basketball statistics.
To illustrate the Hollinger approach, let's take the point value of a blocked shot.
Blocked shots have value where they are rebounded by the defensive team, and where they are, they generally have the value of one possession (i.e. the point value of one possession). This is because the opponent has spent a possession, and received no points. So a player's blocks are valued as
Blocked Shots * VOP * league DRB%
Where "VOP" is the average value of one possession (almost exactly one point to date in 2003/04... 1.0012 points to be exact) and "league DRB%" is the percentage of rebounds that are grabbed by the defensive team - 71.3% in 2003/04 to date.
Point values for other events are similar. The value of a steal, is one possession (i.e., simply VOP). The value of a defensive rebound, is the VOP times (1 - league DRB%)... i.e. the chance that the offense would have grabbed that board.
The value of a personal foul, is more complex, but is essentially the value of the free throws which are generated by the foul. You take the average number of free throws generated by each personal foul, and multiply that by the value of those free throws (minus the "possession value" of the free throws), to get the negative value of a foul.
Add it all up, and you get the contributions of a defensive player, measured in points. You then need to adjust each player for the pace his team plays at. Once you've done that, you have IDV.
Adjusted Defensive Value
The second stat is called Adjusted Defensive Value (ADV) and it is, as the title implies, IDV along with an adjustment. The adjustment in this case has to do with team field-goal defense; it gives players who play on teams with good FG% defense a boost. Essentially, a player gets credit for his percentage of the field goal misses by opponents, keyed to his time on the floor.
The value of a field goal miss generally (to the defensive team) is the same as that of a blocked shot. We figure the number of misses a team forced, subtract the number of misses an average team would have forced, assign the blocked shot value for each miss (a forced miss works the same as a block), then divide up the team's points among all its players based on minutes played. That amount, when added to a player's IDV, is his ADV. I prefer ADV to IDV because though the adjustment amount is usually very small, it does give players on good defensive teams a boost. The largest ADV adjustments for this year are Tracy McGrady (-12.95) and the wholly undeserving Cuttino Mobley (+18.81). Rockets and Spurs players get the biggest boost (thanks largely to Yao and Tim Duncan) and Magic and Blazers players take the biggest hits.
So who are the NBA's best players in Adjusted Defensive Value in 2003/04?
Top 15 in ADV (All data calculated as of February 7)
ADV/48 Minutes (Min 400 minutes)
Well, the 14 guys on these lists are all superb defensive players, really. If you were looking for an All-Defensive team, most of these guys would be on your shortlist, though the list is dominated by shotblocker/rebounders.
The top 5 guards in ADV/48 minutes (min 400 minutes)
Anyway, Shawn Marion plays some guard as well, enough for All-Defensive consideration. (An All-Defensive team might have a token guard, but really the best team defenders in the game are all frontline players).
My All-Defensive Team for 2003/04 so far, then, is Ben Wallace, Kevin Garnett, Andrei Kirilenko, Shawn Marion, and Jason Kidd. Sure, it's hard on Tim Duncan, but ultimately I'd rather have Garnett or Wallace doing my dirty work as the last man back. Call it a personal preference.
My Second Team would be Pierce, Ginobili (with some misgivings), O'Neal, Camby, and Duncan.
The worst twelve players in ADV/48 minutes (min 400 minutes)
I don't know if this last list is really terrible defensively, though it is full of forwards who are hopeless rebounders (Fortson excepted) and who foul a lot (Fortson in spades). Some of these guys (Fortson, Wilcox, Bell) are good enough on the offensive end to be good players overall, and most of the rest (Williamson, Lopez, Lue, Smith, Collins, Korver) are at least decent.
Curry, of course, has the unique distinction of being the worst offensive *and* the worst defensive player to receive significant minutes in the NBA this year. (If you'd seen him play twice a week like I have, you'd know why I say "of course".) I think it's safe to say that's never been done before, and we'll see if he makes it. Curry's actually not a bad man-on-man defender; he's pretty good. But he just doesn't contribute anything at all on the defensive end in terms of making plays, and is the league's worst rebounding forward by miles. If Kevin Garnett is the ultimate impact player, then Curry is his exact opposite.
Incidentally, look for me in an upcoming Aaron's Baseball Blog discussing more basketball-related stuff.
Individual Defensive Value
The first is called Individual Defensive Value (IDV). IDV is simply the total point value of the defensive events that a player is responsible for... his blocked shots, steals, defensive rebounds, and his personal fouls.
How do you determine the point value of a defensive event? For these formulae, I am indebted to John Hollinger and his terrific book Pro Basketball Prospectus. A less modest man than John would have called his book The Hidden Game of Basketball, because his work has had at least that much impact in terms of revolutionizing the study of basketball statistics.
To illustrate the Hollinger approach, let's take the point value of a blocked shot.
Blocked shots have value where they are rebounded by the defensive team, and where they are, they generally have the value of one possession (i.e. the point value of one possession). This is because the opponent has spent a possession, and received no points. So a player's blocks are valued as
Blocked Shots * VOP * league DRB%
Where "VOP" is the average value of one possession (almost exactly one point to date in 2003/04... 1.0012 points to be exact) and "league DRB%" is the percentage of rebounds that are grabbed by the defensive team - 71.3% in 2003/04 to date.
Point values for other events are similar. The value of a steal, is one possession (i.e., simply VOP). The value of a defensive rebound, is the VOP times (1 - league DRB%)... i.e. the chance that the offense would have grabbed that board.
The value of a personal foul, is more complex, but is essentially the value of the free throws which are generated by the foul. You take the average number of free throws generated by each personal foul, and multiply that by the value of those free throws (minus the "possession value" of the free throws), to get the negative value of a foul.
Add it all up, and you get the contributions of a defensive player, measured in points. You then need to adjust each player for the pace his team plays at. Once you've done that, you have IDV.
Adjusted Defensive Value
The second stat is called Adjusted Defensive Value (ADV) and it is, as the title implies, IDV along with an adjustment. The adjustment in this case has to do with team field-goal defense; it gives players who play on teams with good FG% defense a boost. Essentially, a player gets credit for his percentage of the field goal misses by opponents, keyed to his time on the floor.
The value of a field goal miss generally (to the defensive team) is the same as that of a blocked shot. We figure the number of misses a team forced, subtract the number of misses an average team would have forced, assign the blocked shot value for each miss (a forced miss works the same as a block), then divide up the team's points among all its players based on minutes played. That amount, when added to a player's IDV, is his ADV. I prefer ADV to IDV because though the adjustment amount is usually very small, it does give players on good defensive teams a boost. The largest ADV adjustments for this year are Tracy McGrady (-12.95) and the wholly undeserving Cuttino Mobley (+18.81). Rockets and Spurs players get the biggest boost (thanks largely to Yao and Tim Duncan) and Magic and Blazers players take the biggest hits.
So who are the NBA's best players in Adjusted Defensive Value in 2003/04?
Top 15 in ADV (All data calculated as of February 7)
Ben Wallace DET 307.9
Kevin Garnett MIN 262.3
Tim Duncan SAN 245.9
Andrei Kirilenko UTA 225.2
Shawn Marion PHO 207.1
Jermaine O'Neal IND 193.1
Marcus Camby DEN 176.2
Donyell Marshall TOR 167.2
Theo Ratliff ATL 159.8
Ron Artest IND 153.7
Kenyon Martin NJN 147.9
Paul Pierce BOS 145.0
Lamar Odom MIA 142.6
Jason Kidd NJN 135.9
Carlos Boozer CLE 135.7
Yao Ming HOU 134.0
Rados Nesterovic SAN 131.5
Erick Dampier GSW 128.3
Dirk Nowitzki DAL 127.6
Brad Miller SAC 126.8
ADV/48 Minutes (Min 400 minutes)
Wallace 7.49
Duncan 6.46
Garnett 6.45
Chris Andersen DEN 6.44
Camby 6.41
Kirilenko 6.35
Dan Gadzuric MIL 5.40
O'Neal 5.20
Shawn Bradley DAL 4.87
Marion 4.86
Martin 4.83
Theo Ratliff PHI 4.82
Marshall 4.81
Well, the 14 guys on these lists are all superb defensive players, really. If you were looking for an All-Defensive team, most of these guys would be on your shortlist, though the list is dominated by shotblocker/rebounders.
The top 5 guards in ADV/48 minutes (min 400 minutes)
Brevin Knight WAS 4.03
Manu Ginobili SAN 3.90
Jason Kidd NJN 3.71
Paul Pierce BOS 3.55
Darrell Armstrong NOR 3.54
Anyway, Shawn Marion plays some guard as well, enough for All-Defensive consideration. (An All-Defensive team might have a token guard, but really the best team defenders in the game are all frontline players).
My All-Defensive Team for 2003/04 so far, then, is Ben Wallace, Kevin Garnett, Andrei Kirilenko, Shawn Marion, and Jason Kidd. Sure, it's hard on Tim Duncan, but ultimately I'd rather have Garnett or Wallace doing my dirty work as the last man back. Call it a personal preference.
My Second Team would be Pierce, Ginobili (with some misgivings), O'Neal, Camby, and Duncan.
The worst twelve players in ADV/48 minutes (min 400 minutes)
Michael Curry TOR -0.08
Danny Fortson DAL 0.10
Steve Smith NOR 0.14
Jarron Collins UTA 0.24
Tyronn Lue ORL 0.40
Othel. Harrington NYK 0.43
Kyle Korver PHI 0.58
Chris Wilcox LAC 0.67
Raja Bell UTA 0.73
Corl. Williamson DET 0.74
Tony Massenburg SAC 0.75
Chris Wilcox LAC 0.77
Raul Lopez UTA 0.81
I don't know if this last list is really terrible defensively, though it is full of forwards who are hopeless rebounders (Fortson excepted) and who foul a lot (Fortson in spades). Some of these guys (Fortson, Wilcox, Bell) are good enough on the offensive end to be good players overall, and most of the rest (Williamson, Lopez, Lue, Smith, Collins, Korver) are at least decent.
Curry, of course, has the unique distinction of being the worst offensive *and* the worst defensive player to receive significant minutes in the NBA this year. (If you'd seen him play twice a week like I have, you'd know why I say "of course".) I think it's safe to say that's never been done before, and we'll see if he makes it. Curry's actually not a bad man-on-man defender; he's pretty good. But he just doesn't contribute anything at all on the defensive end in terms of making plays, and is the league's worst rebounding forward by miles. If Kevin Garnett is the ultimate impact player, then Curry is his exact opposite.
