Defensive Enlightenment: Help and Double Team Defense

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We continue our introduction of new Vantage Stats that correct many of the problems inherent in using traditional statistics by looking at Help and Double Team Defense. For an overview of our project, please read our post on On-Ball & Screen Defense.   As a reminder, we will introduce new statistics in the following categories:

1) Scoring
2) Facilitation
3) Rebounding
4) Screening
5) Turnovers and Fouling
6) Shot Defense
7) Disruptions
8) On-Ball/Screen Defense:

• Keep in Front % (KIF%)
• Close Out Points Allowed
• Points Allowed Per Screen
• Effective Screen Defense Rate

9) Help/Double Team Defense
10) Movement and Involvement

We are using data gathered at the recently completed Portsmouth Invitational Tournament (PIT) to illustrate the Vantage Stats.


Double Team/Help Defense 

Efficient team defense is dependent on the ability of the players on the court to act in concert helping after No Keep in Fronts (see On-Ball/Screen Defense), double teaming with speed and purpose, and closing out quickly on shooters. Vantage Stats measure the frequency and effectiveness of these skills.

Help Defense arises after a No Keep in Front by a teammate as the player attempts to stop penetration. Effective Help consists of keeping the offensive player in front, stopping scores, contesting shots, and disallowing assists, passes to missed open shots and crucial passes leading to assists/missed open shots (we call these four types of passes combined, Assist+).

Double Teams arise when a defender affirmatively moves to guard an offensive player who is already being guarded.  Similar to Helps, an effective Double Team prevents the offense from scoring or getting an Assist+.  Vantage Stats include parallel stats for both Double Team and Help, including Double Teams/Help Per 100 Chances, Points Allowed Per Double Team/Help, and Effective Double Team/Help Rate.

Double Teams/Helps Per 100 Chances

Double Teams/Helps Per 100 Chances is simply the number of Double Teams or Helps per 100 defensive chances. It measures a player's ability to play off the ball and recognize when a Double Team or Help is needed.

Points Allowed Per Double Team/Help 

Points Allowed Per Double Team/Help measures just the points allowed during a Double Team or Help.  A high number here means that the player is failing in his first responsibility, which is not allowing the offensive player to score during a Double Team or Help.

Effective Double Team/Help Rate

Effective Double Team/Help Rate is a broader measure that includes ineffective outcomes beyond just scoring, such as times when the player fouls and when he allows an Assist+ (see above for definition).

PIT Analysis of Help Defense

For the remainder of this post, we will focus only on Help Defense, as there were limited Double Team attempts during PIT (not surprising for defenses that had never played together and for defenders focused more on showing off their individual skill), but each of the following stats applies in the same way to Double Teams.  Here are the 11 most active (highest Helps Per 100 Chances) help defenders at PIT along with their Points Allowed Per Help and their Effective Help Rate:

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The tape shows the different styles of Help Defense of Jack Cooley (Notre Dame) and Reginald Buckner (Mississippi).  Cooley is usually in better pre-Help position, which allows him to help faster and force the dribbler into quicker decision-making.  However, this solid positioning is not accompanied by much athleticism and shot contesting.  On the other hand, Buckner is usually in worse pre-Help position, meaning he has to move farther to provide help.  However, Buckner is more athletic and is able to help quickly and contest a lot of shots (indeed, he boasted the highest Contest+ and Blocks Per 100 Chances in the tournament, which we'll detail in our Shot Defense post).

Overall, Buckner is the better help defender and shows the most upside if he learns to stay in better pre-help position and not rely so much on his athleticism.

Vantage Stats You Need To Know: On-Ball & Screen Defense

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A New Era

Statistics are important because they tell stories.  Stories about how much we should value players, whom we should praise (or ridicule) and how players are most (and least) effective.  Vantage Sports started with the premise that traditional statistics fail to tell the best, most accurate, and most complete stories and therefore fail in their primary purpose.  This failing affects all those with a vested interest in the game, including players, coaches, front-office management, agents, fans, and media.

Over the next few weeks, we will be officially introducing a number of new Vantage Stats for basketball that correct many of the problems inherent in using traditional statistics. We will introduce new statistics in the following categories:

1) Scoring
2) Facilitation
3) Rebounding
4) Screening
5) Turnovers and Fouling
6) Shot Defense
7) Disruptions
8) On-Ball/Screen Defense
9) Help/Double Team Defense
10) Movement and Involvement

Taken together, Vantage Stats represent the next phase of advanced statistics, lending accuracy and objectivity to the most important aspects of basketball.

To illustrate our statistics, we will use data gathered at the recently completed Portsmouth Invitational Tournament (PIT). PIT is a college-seniors-only invite tournament consisting of 4 teams and 12 games. It typically features players on the bubble of earning a professional contract (not necessarily in the NBA).

On-Ball/Screen Defense

Keep in Front % (KIF%)

The ability to keep your man in front of you is critical for any defender. KIF% is the percentage of drive attempts where the defender keeps himself between his man and the basket.  Vantage measures KIFs from isolation, off-screens, and in closeout situations. Teams employing a funneling strategy where they force penetration either middle or baseline will exhibit lower KIF%s, but these teams should see a commensurate rise in their Help Attempt rates (we'll get to Help Attempts in our Help/Double Team post).  

PIT is a great time to judge KIF% because due to lack of practice time, PIT teams do not employ sophisticated defensive schemes and therefore players have no excuse for having a poor KIF%.

Here are the top and bottom 5 guards in KIF% (excluding those with minimal drive attempts guarded):

Top 5 Guards:

Abdul Gaddy (Washington) - 100%
Vincent Council (Providence) - 89%
Malik Story (Nevada) - 83%
Mark Lyons (Arizona) - 83%
Rotnei Clarke (Butler) - 78%

Bottom 5 Guards: 

Ramon Galloway (LaSalle) - 33%
Mike Rosario (Florida) - 30%
A.J. Davis (James Madison) - 29%
Ian Clark (Belmont) - 15%
Rodney McGruder (Kansas State) - 14%

And here are the top and bottom 5 forwards/centers in KIF% (again excluding those with minimal drive attempts guarded):


Top 5 Forwards/Centers: 

O.D. Anosike (Siena) - 89%
Robert Covington (Tennessee State) - 82%
Devin Booker (Clemson) - 74%
Jack Cooley (Notre Dame) - 72%
Jamelle Hagins (Delaware) - 67%

Bottom 5 Forwards/Centers:

Carl Hall (Wichita State) - 47%
Aziz N.Diaye (Washington) - 45%
Brandon Davies (BYU) - 39%
Chris Evans (Kent State) - 33%
Jake Cohen (Davidson) - 21%


One interesting note is that, as a group, the big men faced more than 2x the amount of drive attempts as the guards.  This was due primarily to drive attempts off screens.

Watching the film on these players shows the top guys really getting into a good defensive stance and working their craft.  Abdul Gaddy (Washington) was far from the most athletic player on the court and he struggled in other categories (see Screen Defense below), but he excelled in KIF% by anticipating drive attempts and taking correct angles to keep in front.

On the bottom side, you see a lot of straight legs, forward leans, and reaction rather than anticipation.

The film also confirms how devastating penetration can be in terms of a defense's Contest+ (a stat measuring shot defense quality that we will cover in a later post).

Closeout Points Allowed

This is the number of points allowed per closeout opportunity.  Thus, a higher number illustrates poor (either slow, no hand up, or leaving feet during) closeout technique.    At PIT, here were the best and worst closeout defenders (for players with over 15 opportunities):

Top 5:

Rotnei Clarke (Butler) - .103 points
Ian Clark (Belmont) - .167 points
Mouphtaou Yarou (Villanova) - .227 points
Scott Wood (NC State) - .321 points
Stan Okoye (VMI) - .333 points

Bottom 5:

Brock Motum (Washington State) - .435 points
Jared Berggren (Wisconsin) - .5 points
Brandon Davies (BYU) - .5 points
A.J. Davis (James Madison) - .571 points
Ed Daniel (Murray State) - 1.22 points

Points Allowed Per Screen and Effective Screen Defense Rate

Points Allowed Per Screen is the number of points allowed per screen defended, both on- and off-ball.  Defending the pick-and-roll is only growing in importance and this statistic provides a good starting point for screen defense analysis.  However, even if a score is not allowed, poor screen defense often leads to the offensive player facilitating for others.  Effective Screen Defense Rate is the percentage of screens defended where the offensive player using the screen does not get one of the following outcomes (a) made field goal, (b) missed open shot or (c) Assist+ (assists, passes to missed open shots, passes to shooting fouls).

Here are the players who defended the most screens during PIT along with their respective Points Allowed Per Screen and Effective Screen Defense Rate: 

Defensive Enlightenment 

Efficient defense, like efficient offense, is a function of many significant actions and outcomes by individual players. Brandon Davies earned MVP honors for the tournament and excelled in a number of areas (mainly offensive) that we will cover, but he was in the bottom 5 in both KIF% and Close Out Points Allowed. Since traditional statistics are geared heavily towards offense, this is unsurprising.  The Vantage Stats shown above, KIF%, Closeout Points Allowed, Points Allowed Per Screen, and Effective Screen Defense Rate, start to allow us to evaluate defenders holistically in a way never before possible. In our next post, we will continue to look at the new ways in which we measure these actions and outcomes for Help and Double Team defense.  Stay tuned...

Pick-and-Roll Defense: The Switch

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The pick-and-roll is one of the most common actions you’ll see across the league. How a defense handles the pick-and-roll goes a long way in determining how effective most offenses can be. Using Vantage’s dataset from this season and last, let’s take a look at how teams employ one of the more unique pick-and-roll defenses: the switch.

The table below shows the how NBA teams defend on-ball screens. On most occasions, a defense will provide some level of help (hedging or retreating into the paint), and then expect everyone to recover to their original defensive assignments. The Wizards have employed this strategy the most (72 percent of the time) across this two-year period. A defense can also double team the man coming off of the ball-screen to try to create a turnover or force the ball out of the ball-handler’s hands. This has been most popular with the Bucks, who double team the ball-handler on about 30 percent of ball screens.  Finally, defenses can simply switch on the screen. The defender that gets screened doesn’t try to stick with his man, instead he guards the screener, while the help defender guards the ball-handler. The Knicks lead the league in switches.

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Some coaches don’t like switching because of the mismatches it creates; having your bigs guarding the perimeter and your guards defending the post is not ideal. But depending on your personnel, it can be a good option. If your point guard is too slow to maneuver around screens, switching can be your last resort. If a team is stocked with similarly-sized players and/or a mobile frontcourt, those mismatches created in a switch may not be mismatches after all. Let’s take a look at how often teams are switching and how effective their defenses are.

The table below shows how successful teams are when they switch on pick and rolls. The first column shows how often teams switch ball screens, it’s the same data as in the table above. The next two columns show the results of those switches, whether they be good or bad. For our purposes, we are considering good defensive play to be a forced turnover, a contested shot, or not allowing any event, such as a shot, assist, foul, etc. A bad defensive play is allowing an open shot, a made shot, an assist, or committing a foul. The fourth column shows how often the defense forces a turnover when switching.

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Some takeaways from the data:

• For the most part, the teams that do the most switching are the most successful at it. The Knicks, Warriors, and Nuggets lead the league in ball screen switches and are all above average at defending when they switch. Each team may have different reasons for their switches. The Nuggets have an army of athletic swingmen, which is perfect for switching, while the Knicks point guards can be a bit limited on defense and may have trouble fighting through screens. 
• The Knicks, under Mike Woodson and Mike D’Antoni, have been the the most likely team in the league to switch defensive assignments on a ball screen. This is for good reason, as they are also the team with the most “good” defensive plays on switches. They aren’t masterful at forcing turnovers or contesting shots, they simply don’t allow shots; no event occurs on 52 percent of their switches.
• The Lakers and the Wizards are also quality defenders after switches, but they do it in a different way than the Knicks. Offenses are more likely to get off a shot against Los Angeles or Washington, but these two teams have been the best at contesting those shots.
• The Dwayne Casey’s Raptors are the rarest switchers in the league, but they aren’t particularly bad when they do. Because Andrea Bargnani has struggled so much with help defense, it might be wise to employ more switching to reduce help defense-related mistakes.
• The Bucks and Kings play the worst defense when they switch, but at least Milwaukee has limited the amount of times that they switch. The Kings, on the other hand, switch ball screens an above average amount of the time. After a switch, the Kings give up an open shot to either the ball handler or another player more than 25% of the time.
• The Hawks and Heat are the best at stopping the ball handler from shooting after a switch. Both of these teams have utilized smaller lineups with some success, and having Lebron James, Josh Smith, or Al Horford switching on to your point guard can be much scarier than facing the average big man switch.
• The Grizzlies are the best at forcing turnovers after switches. That should be no surprise, as they are usually among the best in the NBA at forcing turnovers in general. Known for his quickness despite his size, Marc Gasol has forced turnovers on 10 percent of his switches.

Overall, switches are sparingly used across the league, but there are a few teams that utilize it more than others. Looking at lineup data combined with pick-and-roll coverage data could provide a window into how coaches regard the defensive abilities of their players. 

Hedge Against the Machine: How to Limit the Spurs’ Offense

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As the Clippers were handed a decisive 26-point home loss by the Spurs Thursday night, TNT's Reggie Miller and Chris Webber referred to the Spurs' offense as a “machine.” Every player knows where he needs to be, what pass to make, and which open shot to take (yeah, a lot of times they have many in the same possession).

A lot of credit for the Spurs' offense is given to “best point guard in the NBA right now,” Tony Parker, who went for 31 points, 7 assists, and a game high +31 plus/minus on Thursday night. But the key to the machine is clicking on all cylinders: The Spurs' effective use of on- ball screens in the halfcourt.

Using the Vantage data set, we can see how the Spurs’ use of on-ball screens leads to "effective outcomes" (i.e., scores, assists, open shots, passes to open shots, passes to shooting fouls, and shooting fouls).  On the flip side, we also see that when defending against on-ball screens, a more aggressive initial screen defense can limit the dribble penetration of the screen receiver as well as scoring opportunities from role players.

On-ball screens are a major part of the Spurs' production. To start, the screen quality of Spurs' on-ball screens is among the best in the NBA -- Spurs' on-ball screens make contact with or reroute defenders 50.75% of the time (2nd only to Detroit).  Out of the 24.33% of Spurs' on-ball screens that lead to effective outcomes, nearly 15% of those plays are passes to missed open shots, which leads all NBA teams in the Vantage data set.  But the Spurs are top in the league in offensive efficiency.  These stats show how crucial it is for the Spurs' machine to be working together.  The fact that the Spurs are missing a high percentage of open shots in screen situations and yet still are among the best in the league in scoring in these situations illustrates that their efficiency isn't driven by raw scoring prowess but rather by generating so many good looks that they more than make up for their misses.

Tony Parker’s use of on-ball screens aids him in his ability to facilitate the offense. Of the on-ball screens he receives, 81.88% involve not splitting the screen and not refusing the screen, another example of the structured nature of the San Antonio offense. Overall, Parker will pass coming off a no-split, on-ball screen nearly 75% of the time. Out of those screens, Parker generates an effective outcome (assist, crucial pass, pass to open shot, pass to shooting foul) 34.02% of the time. This suggests that a way to limit Parker’s ability to penetrate and find open shooters is to limit his actions when he comes off the screen. Pressuring Parker and forcing him to retreat (which our data set shows he is forced to do only about 8.24% of the time) would help in limiting his ability to feed the machine.

With 59.44% of all of Parker’s on-ball screens received coming from the high post or 2-point wings, an initial screen defense that hedges against on-ball screens may have the most success when defending these court locations. Sampling the entire data set, we can see that hard-show screen defenses lead to ineffective or nonsignificant outcomes 64.1% of the time, as opposed to soft-show and drop-zone defenses, which yield to ineffective or nonsignificant outcomes 61% and 57.39% of the time, respectively. Although hedging can be a more aggressive initial on-ball screen defense, especially against a quick player such as Parker, statistically it allows the fewest field goal attempts against and scores by a player the defender isn’t guarding. Although it may give up the fewest field goal attempts, it gives up the highest field goal percentage (44.96% compared to more frequently used initial screen defenses, playing behind or showing, which give up 38.91% and 34.31%, respectively). The reward with hedging, however, is that the recovery rates are a lot higher, as 70.9% of hedges lead to recovery on secondary screen defense (compared to 61.9% and 58% for drop zone and soft show, respectively).  Thus, the hard hedge allows the defending guard to recover as the primary defender, which limits dribble penetration.  

Ultimately, one way to stop the Spurs is to not allow all of the moving parts of the machine to function according to plan. Through Parker’s facilitation, which has been especially noticeable this season (6^th in the league in assists), it has helped guys such as Matt Bonner and Kawhi Leonard gain All Star weekend recognition as the benefactors of the high-powered offense. Limiting the offense through aggressive screen defense puts more pressure on the ball-handler, while limiting role players’ presence in San Antonio’s offensive schemes. 

Does Greivis Have a Grievance?

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Is it a snub if the NBA leader in assists is not going to the All-Star Game? Ask third-year Hornets point guard Greivis Vasquez, who has been piecing together the best season of his young career and emerged as one of the league’s best facilitators.  In a season that was destined to feature two of the brightest stars from this year’s rookie class, Anthony Davis and Austin Rivers, it’s been Vasquez’s statistical production that has stood out.  But is it too early to compare him to the NBA’s current All-Star point guards?

Good Indirect Facilitator

As discussed here before, we can find ways to measure Vasquez’s facilitating production even in cases that don't result in a box score assist. The Assist+ Ratio is the number of assists to combined crucial passes (i.e., the hockey assist), passes to missed open shots, and passes to shooting fouls, thereby taking the finishing abilities of teammates out of the equation (lower ratio meaning less help from teammates).  The Assist+ to Crucial Passes Ratio is a measure of indirect facilitation (lower ratio meaning more indirect facilitation compared with direct facilitation).  The following chart compares the top seven NBA assist leaders as of February 10, five of whom are 2013 All Stars, using the Vantage data set:

Rockets coach Kevin McHale knows Vasquez’s improvement has helped develop the Hornets’ young offense, saying, “He’s got to be in the top 10 (in the NBA) as far as importance to his team, when you look at the percentage of points he produces either scoring or assisting on or being involved in a play” (emphasis added). The data support McHale’s theory, as Vasquez is third, and in a group that is significantly ahead of the rest, in our indirect facilitation metric.  This suggests that Vasquez moves the ball well in finding his teammates and creates plays even if he's not getting credit in the box score.  The Assist+ Ratio has Vasquez is in the middle of the pack among the NBA assist leaders, which bodes well for his team's young scoring core.

Smart Passer

Another upside to Vasquez as a facilitator is his ability to make smart decisions. Out of our group of seven, Vasquez is second only to Rondo (by 0.002%) in deflected pass percentage, which measures the number of passes deflected divided by total passes made. Looking at turnovers, we can see Vasquez’s ability to avoid turnovers in making his passes. As a general rule, bad pass is the most frequent turnover type for point guards.  Out of the seven assist leaders, Vasquez has the third lowest percentage of turnovers due to bad passes. 

To measure Vasquez’s ability to avoid bad passes in situations where an assist might be attempted, we are able to look at his percentage of turnovers that he commits after his feet have left the ground.  These are usually instances where the point guard decides to make a play that isn’t a shot attempt. Our data show that Vasquez is the best of the group in terms of not turning over the ball while in the air.

There is, however, another way to look at these numbers given the correlation of percentage of in-air turnovers to points per game.  Perhaps Vasquez isn't being as aggressive as he could be in scoring.  There is such a thing as being too good at a stat if it suggests you're not taking enough risks thereby limiting your potential rewards.  In the last part of the season, as the Hornets Pelicans look toward next season, the numbers suggest that Greivis could and should try to penetrate more to create more offensive production.

Areas to Improve

Along with Vasquez’s high assist numbers, there are also high turnover numbers that have come with it. Vasquez has the fifth most turnovers in the NBA, but despite that, he still better than Holiday and Westbrook, who are second and fourth, respectively.  Looking at the forced/unforced turnover ratio (see chart below), Vasquez’s turnovers are more often the result of his forcing the matter rather than mistakes made by his teammates. But, as we saw above, his bad passes do not comprise the majority of his turnovers.  Vasquez’s high turnover numbers are representative of his ball-handling as opposed to his passing.  Where he has struggled most is on lost balls off the dribble and other ball-handling errors, which combined almost equal his bad passes.  The other elite guards are nowhere near this in their turnover numbers.

While Vasquez’s ASS/TO ratio so far this season ranks behind Paul, Parker, and Rondo, for each of these players, we saw an increase in production from their first three seasons.  Likewise, Vasquez has increased steadily during his first three seasons: 2.2, 2.4, and 2.8 (as of 2/10/13).

One notable difference in Vasquez’s game is that he's not quite the scoring threat as the other names on the list.  Vasquez is also different from these point guards in that he is used the least frequently in perimeter isolation plays.  As we saw above, his ball handling needs some work, as does his risk-taking on scoring opportunities, but if he can make the jump to be a little more aggressive and confident, there is room for him to grow into more of an offensive threat in both facilitating and scoring.

Which leaves us with our original question: Is Vasquez being dis'ed by not getting selected as an All Star? Our data show that while Vasquez is indeed an elite passer, he's got some work to do on the scoring side. With five of the seven names mentioned here going to Houston this weekend, it goes to show that in today's NBA, there is more to a point guard than being a good passer.