April 16, 2020 - 8 minutes
The importance of points per trip
A basketball game is made up of alternating trips up the court. In a given game, both teams have roughly equal trips. As a result, 99.9% of games are decided by who has the highest points per trip. Because of this fact, any approach to ranking offensive and defensive performance should center around points per trip (PPT) and defensive points per trip (DPPT), respectively. However, it is still interesting to look at the components of points per trip to determine what contributes to an elite offense.
The components of offense and defense
Both offense and defense have 3 factors determining effectiveness. The combination of these factors makes up the entirety of a team’s points per a trip. The offensive factors are shooting (points per shot), offensive rebounding (offensive rebounding rate) and turnovers (turnover rate). Defensively, we have shooting defense (defensive points per shot), defensive rebounding (defensive rebounding rate) and forced turnovers (forced turnover rate). Generally, offenses or defenses are designed around maximizing some combination of these factors. For instance, a high energy man defense will often focus on forcing turnovers and contesting shots at the cost of offensive rebounding. On the offensive end, an up-tempo offense may favor quick, high percentage, transition shots at the cost of offensive rebounding.
Points per shot are king for determining a strong offense
If we accept that points per a trip (PPT) is the sole determining factor of a strong offense (It is) then the importance of each of the three factors can be assessed relative to PPT. The figure below demonstrates the relationship between each of the three offensive factors and points per trip.
In this particular plot each of the three factors are plotted for each team with relative points per trip on the y-axis. Offensive rebound % is the percentage of missed shots resulting in an offensive rebound. Turnover % is the percentage of possessions ending in a turnover. Stronger offensive teams have higher relative points per a trip. We can see that points per a shot is almost a straight line indicating a strong relationship between PPS and points per trip. The relationship between offensive rebounding and turnover percentage is less strong but still clear.
Using some statistics, we can determine how much each of the three factors contribute to the overall offensive performance. For the more statistically inclined, we perform a linear regression regressing points per trip on the factors. Using the ANOVA table we decompose the percentage of variance explained by the 3 factors. In total 99% of all variation in offense between teams is explained by the three factors meaning they are truly all encompassing. This analysis shows 84% of offense quality is determined by points per shot, 7% is determined by offensive rebounding and 8% is determined by ball security.
Some of the best scoring teams don’t rebound but some do
I am not arguing that offensive rebounding and reducing turnovers does not help an offense but they are not necessary elements of a solid offense. In fact, its becoming increasingly evident that clearing the lane, and subsequently putting yourself at a disadvantage for offensive rebounds, may be optimal to a lane-clogging offensive rebound oriented offense.
|Team||PPS Rank||ORB Rank||TOV Rank||Offense Rank|
The above table shows the top 10 offensive teams in the 2019-2020 season. Their rankings in the three factors are shown. All of these teams shot efficiently but had varying results in terms of rebounding and turnover rates. In fact, BYU who was ranked 7th overall in offense was also in the bottom 20th in the nation in offensive rebounds. Even Dayton who had the second best offense were in the middle of the entire nation in turnovers and barely top 100 in offensive rebounding.
This is not to completely discredit the importance of ball security and rebounding. Notre Dame is a good example of a team who shot and rebounded at an average rate for a major team (77th and 114th respectively) but were 2nd in the nation in ball security and managed to rank 17th overall in offense. However, it is clear that ball security cannot replace horrid shooting. For instance, Seattle ranked 3rd in ball security but 228th overall in offense due to poor shooting. On the offensive rebounding front UNC is a good example of a team who rebounded well (7th in the nation) but ranked poorly in offense (132nd) due to poor shooting (255th).
Defense is also all about shot defense
Using the same analysis as with offense we find that 83% of defensive success is determined by defensive points per shot, 2% is determined by rebounding and 12% is determined by turnovers forced. The reason for defensive rebounds not being important is due to the fact that points per shot allowed is actually heavily correlated with defensive rebounding ability (Correlation = -.55) meaning it is hard to consider it on its own.
The above plot shows each of the 3 defensive factors and their association with defensive points per shot (The lower the better). It is clear the opponents points per shot clearly correlates with points per trip. Defensive rebounding has a weaker relationship and forced turnover percentage has an even weaker relationship. One explanation is that aggressive turnover facing play may for some teams result in a sacrifice in shot defense.
|Team||DPPS Rank||DRB Rank||DTOV Rank||Defense Rank|
|San Diego State||7||103||81||8|
The above table shows the top 10 defenses by relative points per trip. Just like offense, most of the top 10 teams are also in the top 15 in shot defense. The lone exception is number 10 Texas Tech. Texas Tech made into the top 10 by having a relatively strong, but not elite, shooting defense along with strong rebounding while forcing a high amount of turnovers.
Basketball is a game of trade-offs
Barring exceptional talents, teams have to choose which factors to emphasize in a game. Sometimes this is a conscious decision but most of the time it is a side-effect of the system used. For instance, most of the best defensive rebounding teams play zone and the worst offensive rebounding teams play motion offense. As a result, there are no teams who are truly elite at all aspects of offense and defense. The closest this year was Gonzaga on offense (6th in points per shot, 28th in offensive rebounding and 6th in ball security) and Virginia on defense (3rd in defensive points per shot, 9th in defensive rebounds and 52nd in turnovers). These are elite teams with elite talent, it is even harder for mid-majors to achieve this kind of success. As a result, it is becoming increasingly clear that specialization is key for mid-major success and with the evidence above a specialization that emphasizes shooting on both ends of the court is the optimal style.
Offensive trade-offs in action
For empirical evidence of this fact, we can look at the offensive-styles of some of the most consistent mid-majors. Teams like Northern Iowa, Saint Mary’s or Creighton have all found success despite glaring “weaknesses” in their 3 factors. In the 2019-2020 season, Northern Iowa finished 3rd in PPS but 229th in ball security. Meanwhile Saint Mary’s and Creighton both sacrificed offensive rebounding (195th and 258th) in favor of scoring (5th and 10th). BYU is the best example this season finishing 2nd in points per shot and 7th in overall offense while finishing 335th in offensive rebounding. Another good example is South Dakota who performed better offensively than many majors (68th overall) by employing an offense that kept the lanes open and used screens at the top of the key. This style. which is used with success by most of the aforementioned teams, allowing them to shoot effectively (34th overall PPS) at the expense of offensive rebounding (336th).
Defensive trade-offs in action
As we have shown teams who have strong shot defense tend to have strong defensive rebounding. In all likelihood, this is due to the same thing that causes strong shooting teams to generally be poor at offensive rebounding. While strong scoring teams generally operate with open lanes, strong scoring defenses are going to clog the lane. Consequently, the players in the lane will be in position for defensive rebounds. However, aggressive defenses which force turnovers will not be in position for rebounding. As a result, it is rare for a team to be good at both forcing turnovers and rebounding. In fact of the top 10 defensive rebounding teams, only 3 have a forced turnover rate in the top 150.
Unlike offense, the formula for an overachieving defense is less well-defined. Arguably the most overachieving mid-major on the defensive end Ball State (22nd overall defense), played a strict 3-2 zone. However, teams like UNC Greensboro (35th overall defense) found success by forcing turnovers (2nd in the nation) with a high-intensity man defense. Even though we cannot define the perfect defense, it is a fact that any succesful offense limits their opponents shooting ability to some extent. However it is done is up to them.