January 6, 2017 by J.H. Yeh
In the last article (part 1: Field Goal Percentage), we went over that stretching the defense leads to higher field goal percentage and an overall efficient offense. However, we only talked about “efficient offense.” In this article, we will go more in depth about what does it mean for the offense to be “efficient.” An efficient offense means teams are taking high percentage shots. It is established that the most efficient shots are right beneath the basket. However, at times, such shots are not always available, depending on how the offense and defense develop. As a result, teams often look for the next most efficient shots besides the ones taken right below the basket.
Before we delve into efficient offense, let’s talk about shooting range shots. Points can be produced in a variety of ways and range shots are certainly one of the most common ways for teams to accumulate their scores. Range shots can be shot from roughly five regions — paint, mid-range, above the break 3, left corner 3, and right corner 3. We will leave out the elbow and the wing shots as these two shots are the most inefficient (and most difficult) shots to make. We will get to these types of shots another time.
Below is the breakdown for the field goal percentage and the effective field goal percentage for each region for the 2016-17 season. This stat is through as of January 5, 2017, courtesy to NBA’s player tracking data. Note that effective field goal percentage is the same when the shot is taken within the 3-point arc.
The chart shows that besides the restricted area (below the basket), the corner 3s generate the highest effective field goal percentage. If we want to go into a step further, the ideal spot to shoot of the two corners is the right corner 3. This is probably because it’s easier to aim since most players are right-handed. According to the bar chart, the most effective range shots are the corner 3s, and then that is followed by the above the break 3s (top of the key). The least efficient shot is the mid-range shot. The chart above also validates the fact that mid-range shots are not preferred because perimeter shots are far more efficient than those inside the arc and between the paint, which is something we discussed previously (clicker here for that article).
In the past few years, thanks to analytics, teams are starting to trend small and building teams with perimeter shooters to maximize the returns in points. However, not every team is moving towards this direction at the same pace. Teams such the Dallas Mavericks (before they let go all the good players) and the San Antonio Spurs (who are known for utilizing the corner 3s) are the pioneers in employing strategies that run their offense through effective 3-point shootings. The Houston Rockets are the first team to fully take advantage of the 3-point line by heavily favoring shooting 3s and intentionally avoiding running their offense through mid-range shots. The Rockets started such strategy around the 2006-07 season when Morey was hired as the Assistant General Manager (he became the GM a year later). Now let’s look at how the NBA overall has evolved when it comes to shooting mid-range shots versus shooting 3- point shots.
Although not every team is moving towards shooting 3s at the same pace (namely the Memphis Grizzlies), the NBA overall is starting to realize the importance of exploiting the 3-point line by increasing the amount of 3-point shots while decreasing the amount of mid-range shots. The 2014-15 season marks the first time the NBA overall is shooting more 3-point shots than mid-range shots — and such pattern is highly unlikely going to change in the foreseeable future as the game has evolved into a different ball game than what it used to be in the pre-analytics era.
Now we have established that the two most efficient range shots are the corner 3s and the above the break 3s. To sum up, teams should find ways to put the ball into the basket by shooting from right below the basket, from the corners, and from the top of the key. So far all these have aligned with what we discussed in the previous article that stretching the defense can help spacing the floor by creating opportunities to score from the inside and the outside, resulting in more high percentage shots and an overall efficient offense.
We went over where to shoot those range shots. Now let’s look at how to shoot them. There are two ways for a player to shoot a range shot: Pull-ups and catch & shoot. It is widely understood that catch & shoots are preferred because the player is in stationary motion with the body and feet already established on the floor and ready to shoot; whereas, for pull-up shots, the player is often in moving motion and their feet are out of position, which make it challenging to make those type of shots. Now let’s look at how the field goal percentage and the effective field goal percentage of these shots to precisely gauge the true values of pull-ups and catch & shoots.
Whether it’s shooting 2-point jump shots or 3-point field goals, the catch & shoot method yield better efficiency. If we strictly look at the effective field goal percentage, catch & shoots clearly tops pull-ups by a landslide margin 56.0% vs. 41.7%. There is a story behind each saying and this is why high school coaches always stress the importance of practicing catch & shoots. Fortunately, now we have the numbers to back this up.
To sum up, the two most efficient shots outside the restricted area are catch & shoot corner 3s and catch & shoot above the break 3s. With that said, teams should strive to achieve these goals when it comes to executing offense.
Now it finally comes to executing catch & shoots at the perimeter. Stationing perimeter shooters can stretch the defense but that doesn’t mean the players can shoot since they are all guarded by a defender. Being guarded by a defender involves individual skills to create space for shooting for that player — and that is achieved by pull-ups, which is not an efficient shooting method. Due to that reason, teams should avoid running isolation plays, and instead, have other players involved to create space for others. As simple as it sounds, we don’t call basketball a team sport for no reason.
Let’s focus on catch & shoots from the corners. Although this perimeter shot has the shortest distance to the hoop, it is also the hardest to guard because it involves the defense to really spread out far to the corners. Doing so involves driving. Or more specifically, drive and kick (pass) strategy to create space for those corner shooters.
According to basketball analyst and mathematician, Stephen Shea, only 1 in 5 points (20%) is generated from drive and kick strategy. With the league averaging 104.7 points per game and 6.9 points from made corner 3s, this tells us that only 0.67% of total points comes from those made corner 3s. Despite such a small sample, corner 3s prove to be very predictive of effective field goal percentage.
In this scatter chart, I plotted C3FGM/FGA and eFG% together to create a scatter chart to see the correlation between the two and how eFG% is dependent of C3FGM/FGA.
C3FGM/FGA is the amount of made corner 3s divided by total field goal attempts. This provides a better look at the percentage of the made corner 3s out of overall field goal attempts. Teams located at the top like the Rockets are very high in eFG% because they shoot a lot of 3s. The Indiana Pacers, similarly is also strong in both C3FGM/FGA and eFG% because they are a “3 and D” team. The Pacers are strong in both perimeter defense (ranked second in opponent 3FG% at 33.8%) and making 3s from the corner. They are efficiently making 39.4% of all corner 3s. However, their problem is they don’t attempt a lot of these corner 3s despite the high percentage. A lot of their field goals came from mid-range shots which explains why the Pacers are sitting above the line. As part of former head coach Frank Vogel’s legacy, the defensive-oriented Pacers are attempting 24.2 mid-range shots (4th in league) and making 10.2 of those shots (2nd in league).
With a R-squared at 0.58, the linear regression line explains that C3FGM/FGA is closely related to the total offense’s efficiency. The Warriors lie below the line because they are attempting and also making plenty of 3-point field goals outside of the corner 3s, which naturally pulls down their eFG%. The similar can also be applied to the Cleveland Cavaliers. On the other hand, the Minnesota Timberwolves and the Toronto Raptors are the only two teams to be below the average C3FGM/FGA (0.028) but have an eFG% above 0.52. This anomaly is explained by the presence of mid-range forwards in Gorgui Dieng and Patrick Patterson, who are very proficient in making mid-range shots, therefore attributing to their teams’ high eFG%.
Now let’s look at the correlation between C3FGM/FGA and 2FG%. Note that we are just solely focusing on made 2-point field goals instead of the overall effective field goal percentage. Not surprisingly, the two teams sitting on top are the Warriors and the Rockets thanks to their incredible perimeter shooting that successfully aids in floor spacing and allowing many easy looks in the interior. Sitting in the bottom are the Memphis Grizzlies, who do not make a lot from the corners. Their low 2FG% is explained by the big lineup that features old-school post player in Zach Randolph and an offensively creative Marc Gasol, who make the opponent’s defense concentrate in the interior. As a result, due to the lack of floor spacing and offensive focal points in Randolph and Gasol, the two big men have to put up challenging shots on a nightly basis due to the clogged paint and the condensed defense around them. The same also goes to the Chicago Bulls, who also sit close to the bottom. As previously mentioned, the Bulls also face a similar quandary in the lack of floor spacing and too much bodies in the paint which draw heavy interior defense that contributes to overall low offensive efficiency.
Finally, let’s incorporate driving FG% and string everything together. The driving data is elicited from NBA’s player tracking, computed by SportVU’s spatial tracking. According to the NBA, driving is defined as any touch that starts at least 20 feet of the hoop and is dribbled within 10 feet of the hoop and excludes fast breaks. Fast breaks are excluded because the defense is not yet set up; hence, including fastbreaks cannot accurately reflect the team’s offensive efficiency. Driving FG% is achieved when a player makes a shot while in the act of driving. These types of shots are layups, dunks, and floaters inside the paint.
Again, not surprisingly, with the team’s 2FG% at 0.563, the Warriors are leading all teams because they are very proficient in both shooting 3s and driving into the basket. Other teams that sit above the trend line include the Rockets and the Cavaliers. The San Antonio Spurs, known for finding the open men to shoot, also sits above the line because they are shooting more than driving into the basket. On the contrary, the Bulls sit far below the line because they are driving more and shooting less. What’s worse is that not only do they drive more, they are also inefficient at making those driving shots because the opponents are tightening their defense in the interior since the Bulls are very poor at making 3s to a degree that opponents simply ignore their shooters and just solely focus on interior defense. In a way, the Bulls’ abysmal perimeter shooting is aiding the opponents’ defensive strategy as putting a defender on the perimeter is just as good as not putting a defender on the perimeter. As expected, the Grizzlies also sit at the very bottom because not only they don’t drive a lot into the basket, their offense revolves around Randolph and Gasol, two big men who are too slow to drive. Unlike the Grizzlies, the Bulls have at least Dwyane Wade, Rajon Rondo, and Jimmy Butler who are smaller and a lot more agile and quicker to drive and power their ways into the paint.
Conclusively, having perimeter shooters can help stretching the defense, which, in turn, can improve offensive efficiency because it gives more spacing on the court for players to drive. Concentrating on scoring from the two most efficient shots, right below the basket and the corner 3s, is best done through drive and kick strategy as evidenced by the charts. The positive correlations between 1) the corner 3 and eFG%, 2) the corner 3 and 2FG%, and 3) the driving FG% and eFG%, further confirm that stretching the floor with shooters allows the offense to have room to drive for an easy layup, or pass to a cutting player, or pass to the corner shooter for an uncontestd catch & shoot 3. For another word, defensive inefficiency should be taken advantaged of by utilizing the drive and kick strategy to create space on the floor for open men before the defense can recover.
A quintessential example is the 2011 NBA Finals. With the underdog, the Dallas Mavericks featuring three floor spacers as the starters in Dirk Nowitzki, Jason Kidd, DeShawn Stevenson, and with shooters Peja Stojakovic and Jason Terry coming off the bench, the Mavericks found themselves in trouble. Despite having ample shooters on the floor at all time, the Mavericks had difficulty with passing the ball to the open men against the quicker and younger Miami team. Losing two of the first three contests, Rick Carlisle replaced Stevenson with J.J. Barea, who is quick and effective in driving into the paint. This change in the starting lineup created more space for drives and catch & shoot opportunities for the Mavericks, which ultimately won the next three games in a row and went on to win the franchise’s first NBA Championship.
As a result, stretch in defense can improve offensive efficiency because it allows more room for players to drive, pass the ball to a cutting player, or find mismatch and post up. Doing so also causes defensive inefficiency and allows the offense to find an open player at the corner 3 for a catch & shoot before the contracted defense can spread out again and recover.
— J.H. Yeh
(all graphs are created by me, and all sources of stats are courtesy of NBA.com and BasketballReference.com as of January 5, 2017)