Preliminary Investigation into Defensive Stretch

By Stephen Shea (@SteveShea33) and Chris Baker (@ChrisBakerAM)

September 14, 2015

 

On May 10, 2015 (after the now famous “goink” text), Phil Jackson tweeted, “Seriously, bball, it’s about penetration.”

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Phil is correct. Great offenses find ways to get to the hoop. Great defenses find ways to stop that penetration.

SportVU’s spatial tracking system in the NBA provides the positions of all players and the ball multiple times a second. This new information gives us the chance to study, in an objective and efficient manner, the spacing and formation of lineups as they attempt to score or defend on a possession.

In regards to Phil’s tweet, we can finally begin to understand how teams create lanes to penetrate. We can actually measure the extent to which an offense stretches a defense.

In Basketball Analytics: Spatial Tracking, we introduced the idea of CHAD (the Convex Hull Area of the Defense). Consider the image below taken from an NBA.com movement animation. It is the 3rd quarter of the Clippers-Warriors game on March 31, 2015. Notice the blue polygon wrapped around the Clippers’ defenders and the red polygon wrapped around the offensive players. The area of the blue polygon is CHAD, and the area of the red polygon corresponds to what we called the Convex Hull Area of the Offense (or CHAO).

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A large CHAO means the offense is spread out. A large CHAD means the defense is stretched, and a stretched defense is more vulnerable to penetration and attacks at the rim. In the image above, the Clippers’ defense is stretched far to the perimeter. Their CHAD is large.

The second image below was taken from a Knicks-Clippers game on March 25th.  Here, the Knicks are well spaced. Their area (or CHAO) is large. However, the Clippers have a very small defensive area. They are in great position to defend the rim (and are ignoring the players on the perimeter). The Clippers are ignoring the Knicks on the perimeter because those Knicks aren’t the best shooters. Shane Larkin is #0. He shot 30% from three in 2015. Lance Thomas is #42. He only took 21 3-point attempts. Langston Galloway (#2) is the best of the bunch. He shot 35.2% on the season. As a relative newcomer, the Clippers may not be showing his shot the respect it deserves.

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For the 2015 season, we froze the game at the first point of every halfcourt possession when the ball was on the 3-point line above the break.   For our halfcourt possessions, we required all 10 players to be in the halfcourt and the defense to be set. We then measured the CHAO and CHAD. As we expected, the lineups that typically stretched the defense were also very successful and efficient.

Here are the top 5 offensive lineups in average CHAD against (among lineups with a minimum of 100 possessions in our query):

  1. Clippers: Chris Paul, J.J. Redick, Matt Barnes, Spencer Hawes, DeAndre Jordan
  2. Warriors: Steph Curry, Klay Thompson, Andre Iguodala, Draymond Green, Marreese Speights
  3. Warriors: Steph Curry, Klay Thompson, Harrison Barnes, Draymond Green, Marreese Speights
  4. Cavaliers: Kyrie Irving, J.R. Smith, LeBron James, Kevin Love, Timofey Mozgov
  5. Warriors: Steph Curry, Klay Thompson, Andre Iguodala, Draymond Green, Andrew Bogut

According the NBA.com, these lineups averaged between 113.3 and 124.4 points per 100 possessions.

Here are the bottom 5 lineups (with the lowest first):

  1. Wizards: John Wall, Garrett Temple, Paul Pierce, Nene Hilario, Marcin Gortat
  2. Timberwolves: Ricky Rubio, Kevin Martin, Andrew Wiggins, Thaddeus Young, Nikola Pekovic
  3. Nets: Deron Williams, Joe Johnson, Markel Brown, Thaddeus Young, Brook Lopez
  4. Pistons: Brandon Jennings, Kentavious Caldwell-Pope, Kyle Singler, Greg Monroe, Andre Drummond
  5. Hornets: Kemba Walker, Gerald Henderson, Lance Stephenson, Cody Zeller, Al Jefferson

According to NBA.com, these lineups averaged between 93.3 and 109.9 points per 100 possessions.

As for Phil’s Knicks, injuries and trades shuffled the roster enough to leave small samples on their lineups. As a team, they had the 6th lowest average CHAD and the lowest CHAO.

It’s tough to penetrate, when there is no space around the hoop. Perhaps this is why the Knicks made the NBA’s fewest field goals per game from within 5 feet (13.4).

As the title suggests, all of the above is a preliminary investigation into defensive stretch and how teams space the floor.  Simply looking at spacing at the start of possessions provides an incomplete picture of how a team runs its offense.  We’ll dig deeper as we approach the start of the 2015-16 season.

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6 Comments

  1. Great post guys. It’s both interesting and informative. Just a heads up, Larkin and Lance Thomas’ numbers are flip flopped. Larkin wore #0.

    Reply
  2. Angel Macedon

     /  March 17, 2016

    This makes you wonder what Phil Jackson is doing.That team is not configured to score well outside or inside.

    Reply
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