Pick-and-Roll Defense: The Switch

The pick-and-roll is one of the most common actions youll 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 Vantages dataset from this season and last, lets 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-handlers 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 doesnt 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 dont 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. Lets 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, its 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.

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 DAntoni, 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 arent masterful at forcing turnovers or contesting shots, they simply dont 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 Caseys Raptors are the rarest switchers in the league, but they arent 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.

Jason Collins’ Revelation and the Top Screeners in the NBA

Jason Collins said something last spring that we here at Vantage Sports have been waiting to hear an NBA player admit for a long time. Spoiler alert – it had nothing to do with his sexual orientation.

“My contributions don’t show up in the box scores.”  

What Collins meant is that his game involves moves that improve other players’ box scores. As he explains, “I set picks with my 7-foot, 255-pound body to get guys like Jason Kidd, John Wall and Paul Pierce open.”

Screens are crucial to every team’s success. Screens are the only tool a player has to legally contact a defender, creating space for a teammate to either score or facilitate a score. Collins’s abilities have been rewarded with an NBA salary for more than a decade, yet have never been effectively tracked or measured.  Notice that there is no “effective screens” line item in your NBA box score. Vantage Stats changes that by measuring both screening effort and efficiency.

Solid Screen % and Screens Per Chance

A good screen requires more than a big body (or as John Stockton proved, a not-so-big body).  The fundamental job of the screener is to create space either through contacting the defender or forcing the defender to adjust his path.

Vantage tracks a player’s “Solid Screen %”. This is the percentage of set screens (both on-ball and off-ball) where a player either makes contact with a defender, or re-routes that defender.  This statistic excludes slip screens (times where the screener rolled or popped prior to the receiver getting to the screen).

Here are the top 5 NBA big men in Solid Screen % over the past two seasons (with minimum offensive chances and screen attempts) along with their Screens Set Per Chance:

1. Ronny Turiaf (79% Solid) (.49 per chance)
2. Nick Collison (78.3% Solid) (.44 per chance)
3. Marcin Gortat (78% Solid) (.63 per chance)
4. Joakim Noah (77.5% Solid) (.47 per chance)
5. Kenyon Martin (77.2% Solid) (.42 per chance)

Set Screen Points Per Chance 

“Set Screen Points Per Chance” is the number of points per offensive chance created by player’s set screens.  This is the cash-out value of a player’s set screens in terms of points scored by his teammates. Another way to think of this statistic is like a non-passing assist.
 

Here are the top 5 NBA bigs in Set Screen Points Per Chance over the past two seasons (again, with minimum offensive chances and screen attempts):

1. Tiago Splitter (.123 points per chance)
2. Kendrick Perkins (.117 points per chance)
3. Joel Anthony (.11 points per chance)
4. Tyson Chandler (.108 points per chance)

5. Marcin Gortat (.107 points per chance)

Your mind is probably jumping ahead of itself at this point, thinking about the scorers using those screens, right? Indeed, Tony Parker’s uncanny/gymnastic/otherworldly scoring ability might be inflating Splitter’s numbers here. And full disclosure: Duncan is #6.

This metric therefore suffers from the same bias that box-score assists do. You can’t control your teammates’ ability to hit shots in open space, and those that are surrounded by great scorers are going to look like better screeners in this context. But combined with other metrics, this can be a powerful signal in evaluating underlying factors of offensive efficiency.

Set Screen Outcome Efficiency

One way to correct “Set Screen Points Per Chance” is to look at screens leading to a more broadly defined set of “good” outcomes.  “Set Screen Outcome Efficiency” does exactly that.  It is the percentage of set screens that result in a teammate score, missed open shot, shooting foul or Assist+ (see our earlier post on passing).
 
Here are the top 5 in Set Screen Outcome Efficiency (again, adjusted for minimum offensive chances and screen attempts):
 
1. Carl Landry (49%)
2. Joakim Noah (48%)
3. Andrew Bynum (47.9%)
4. Jason Maxiell (44.8%)
5. Kendrick Perkins (44.7%)

Putting It All Together: Noah Is the Best

3 names appear twice in the 3 lists above, Joakim Noah is in the top 5 in both Solid Screen and Outcome Efficiency. Marcin Gortat is in the top 5 in Solid Screen and Points Per Chance. Finally, Kendrick Perkins is in the top 5 in Efficiency and Points.

 
Noah’s Points Per Chance is at .064, which is nowhere near the leaders in that category. However, he stands out as the best high volume screener in the league.  This is because Set Screen Outcome Efficiency is more screener-dependent than Points Per Chance and the best way to judge screen value independent of teammates’ performance. Noah excels in setting solid picks resulting in good outcomes for the Bulls.  With Derrick Rose back on the court look for Noah’s Points Per Chance number to jump.
 

Here are a few Noah highlights to get you ready for the season:

Conclusion

Statistics are important because they tell stories. Stories about how much we should value players, who 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 most compelling stories.

Vantage Stats aims to improve the ability to measure performance and track the most meaningful aspects of the games we love. We hope the Jason Collins of 2016 can say, “Clearly, you should sign me. My Solid Screen %, Screen Points Per Chance, AND Set Screen Outcome Efficiency are all off the charts!” In case you were wondering, though he didn’t have the sample size to make it, the Jason Collins of 2012 was a very good screener, posting an 82% Solid, .069 Points Per Chance and 39.5% Outcome Efficiency.

The Corner Three

Of all the potential shot attempts, a three-pointer from the corner is one of the best shots an offense can get. Across the league, players shoot at a higher percentage from the corner than from other spots around the three-point arc. One obvious reason is that it is the shortest distance three-pointer available. But what about other factors that can affect shooting percentages, such as how the defense reacts to the shot or whether the shooters’ feet are set? Using Vantages dataset from this season and last season lets take a look at how shot defense and shooter movement change from different spots around the three-point arc.

Shot Defense

Because of some teams defensive rotations and their willingness to leave certain shooters alone in the corner, it is worth investigating whether the average corner three is met with less defensive resistance than other threes. If corner three-point shooters are getting wide open looks while shooters from other locations are getting their shots contested, then that could help explain why players hit corner threes at such a high rate. The corner three might not be that easy, its just that defenses are giving up open shots in the corner and guarding the threes around the wings and top of the key.

The chart below shows how often shooters from the different locations see various levels of a shot defense.  “Contest+” includes when defenders block the shot, alter the shot, or are within three feet of the shooter with their hand up. “Pressured” indicates when the defender is within three feet of the shooter without a hand up, “Guarded” is in between three and five feet of the shooter, and “Open” is when a defender is outside five feet.

As the chart shows, defenses are challenging shots in almost the exact same ways from each of the locations. Regardless of location, roughly half of three-point attempts are strongly contested, and the other half are split about evenly among the remaining categories. So we know that defenses aren’t forgetting to contest three point shots, even when they are being launched from the corner.

To further explore the numbers, here are the shooting percentages by location and level of shot defense.

When defenses are strongly contesting the shot, the corner three loses some of its appeal. Shooters are hitting 33 percent of their strongly contested corner threes, about the same as a three from the wing. However, once the level of defense drops off, the corner three gets much more dangerous. When a defender simply can’t get a hand in the face of a corner shooter, the percentages jump up to 38 percent and continue rising above 40 percent as the defense gets worse. On threes from the wing and top of the key, the percentages don’t start looking good until the defense gets really lax.

Number of Dribbles

Another reason corner threes may be generally easier than threes from other locations is that a player is highly likely to have his feet set prior to shooting when he is in the corner. Most players are much more comfortable taking jumpers with their feet set, as opposed to off the dribble. The chart below shows how often players are using their dribbles when taking jumpers from the three-point locations.

Less than five percent of corner threes are shot off the dribble. That number pales in comparison to threes from the top of the key and wing, where 37 percent and 22 percent of threes are taken off the dribble, respectively. Obviously, there is more room to move on the wings and top of the key than in the corner, so we are more likely to see shots off the dribble, with players using ball screens, crossovers, etc.

When we look at the three-point percentages by the number of dribbles, we can see that when players don’t need to dribble, the corner three is still made at the highest rate (38 percent).

The wing three is close, at 36 percent, but the corner three still reigns supreme in terms of efficiency. Once a shooter starts dribbling, those percentages drop. While shooting off the dribble decreases percentages in any of the locations, nowhere is it more drastic than from the corner. On the rare occasion that a corner three is taken off the dribble, they are only going in 25 percent of the time. Unless its Kobe Bryant in his prime, dribbling into the corner is usually a bad idea.

If dribbling is eliminated from the equation and we only look at the difficulty of zero-dribble threes, the chart looks like this:

Conclusion

Even after accounting for shooter movement and the strength of the defense, the corner three still comes out looking like the easiest three. The big difference with the short distance corner three comes when defenders aren’t playing strong defense. If a shot is launched from the wing or top of the key, the defense might be able to get away with not getting a hand up. But if that three-point attempt comes from the corner, anything but a great defense can turn an average shooter into a 40+ percent shooter.