Possession and Points Swing: Why it Matters
Updated: Dec 19, 2019
Why it is important to control the ball and swing possessions/points to your team
In sports, possession is everything. “Possession”, or “opportunity to score,” is so essential that it is often a less cloudy picture of what is going on than actually scoring.
“Time of possession” is an important metric in football and soccer. It’s no surprise that if your team is “in possession” more than the opponent that it increases your odds to score points and ultimately win the game.
“Serve Attempts” in volleyball, “On Base Percentage” in baseball, and “Fenwick Possession” in hockey are tools to identify how the opportunities to score (possessions) have been spread between the teams.
In basketball, possessions are generally spread evenly. A made shot my Team A closes their possession and a new one starts for Team B that can close in a variety of ways, such as a made shot attempt, a rebounded shot attempt by the defense, free throw attempt(s), and turnovers.
As previously explained, possessions are designed as opportunities to score. A turnover ends a possession without an opportunity to score. An offensive rebound extends a possession (or robs a possession from the other team).
These actions, turnovers and offensive rebounds, “swing” possessions.
The ability to force a turnover by your opponent swings that possession to your team. A positive possession is awarded your team. Allowing an offensive rebound to your opponent swings that possession to the other team. A negative possession is awarded your team.
The total net difference of turnovers and offensive rebounds at the end of the call we call the “Possession Swing”. A positive swing means your team had more possessions swung in their favor than the opponent (hence more opportunities to score).
Yet, as important as it is to swing possessions your team’s way, the real goal of each possession is to score.
Points off of turnovers your team forces and 2nd chance points off of your team’s offensive rebounds are points off of swung possessions. The net difference between these points and the points scored by your opponent from swung possessions we call “Points Swing”.
These metrics are an additional lens to evaluate performance, and aid shooting metrics (like Effective Field Goal Percentage - eFG%) in explaining game results,.
Take last night’s action for example:
Denver beat Portland 114-99. Denver shot 5% eFG
over the coarse of the night. Most analysts would say (rightfully so) that the shooting was the difference. It was, but it wasn’t a big enough difference to explain the blowout.
Denver had a +6 Poss Swing (8 more OREBs than Portland, 2 fewer TOVs). They had six more opportunities to score than their opponent. What did they do with those extra possessions?
Denver had a +11 Points Swing (5 more points off OREBs than Portland, 6 more points of TOVs). Denver was able to turn their six extra possessions into 11 extra points. That explains the blowout.
This system can be used game to game, or can be used on a macro level to analyze the league. Take a look at the below chart for a Points Swing and Poss Swing per game look at the entire league:
Viewing the results of this chart in conjunction with what we know about the shooting prowess of each team explains a lot about how the league has performed thus far.
MIL and LAL are the best teams. Why? They are the two best shooting teams, yes, but they also have +5.7 poings swung in their favor every night on extra possessions swung to their teams. It’s hard to beat teams that can do that.
DEN and UTA are 11th and 12th respectively in NRTG this year. DEN is 25th in shooting while UTA is 9th. What’s the difference? DEN has a positive Poss Swing and a +3.4 Pts Swing per game. UTA has a negative Poss Swing and a -5.9 Pts Swing per game.
NOP shoots the ball well (9th in the league) but can’t put it together. They have a -0.1 Poss Swing per game. They have as many extra opportunities as their opponent. But at a -5.0 Pts Swing, they aren’t taking advantage of extra possessions.
MIA is shooting better than expected. Their negative Poss and Pts Swing is concerning should their eFG% come back to earth.
Pts Swing and Poss Swing don’t tell all of the story. They are not as good of indicators as NRTG or even eFG%. But they do show how important the other 4 Factors are on the game.
This is explained well in the example of UTA’s narrow loss in MIL 118-122:
UTA had one of its best offensive games of the year, shooting a scorching 63% eFG to MIL’s 51%. Without seeing the final score, you’d assume UTA beat MIL. Most of the time you’d be right...but not on this game.
UTA had a -19 Poss Swing in this game. 19 extra possessions went MIL way. Though not on their game that night, if the Bucks get that many more bites at the apple, their sure to get to the core.
And that they did.
UTA allowed a -28 Pts Swing to MIL on 19 extra tries. That was the difference in the game.
On a night with all the shooting in the world and enough shot defense to create a 12% gap in eFG%, the Jazz lost because too many possessions were swung to the Bucks and they capitalized.
The ideal world is to be one of the best shooting teams and have a positive Pts and Poss Swing. But not every team can be like MIL and LAL.
UTA is an excellent example of a team who is underperforming despite having a good defense and excellent shooting. What is to be done.
They need to control the ball...enough.
The Jazz are the worst team in Poss Swing and the second worst in Pts Swing. With as much defense as they have and as good of shooting personnel on their roster, they should be way better.
The good news is they can. The secret is not to shoot better. The first step is to reduce the amount of extra possessions swung to your opponent. This can be done by avoiding turnovers and preventing offensive rebounds, or by forcing more turnovers and collecting more offensive rebounds.
In the end, the Jazz need to work towards an even Poss Swing. Only three teams in the league with an even Poss Swing have a negative Pts Swing. This implies that a team’s Poss Swing will naturally improve their Pts Swing.
The correlation coefficient between Pts Swing and Poss Swing is a 0.73. A 1.00 is a perfect correlation (meaning a perfect relationship). If UTA can improve their Poss Swing, they will improve their Pts Swing.
Teams will continue to win the offhand game with a negative Pts and Poss Swing just as teams will lose games with excellent swings.
But at the end of the day, you must control the ball. And if you have enough shooting, you just have to do i enough.