https://www.poundingtherock.com/2018/9/13/17813602/san-antonio-difficulty-understanding-importance-rebounding

The difficulty in understanding the importance of rebounding
By CharlieOCharles Sep 13, 2018, 9:17pm CDT

... The result is that we know we need to dig a lot deeper into player tracking, lineups, and schemes to really understand what rebound numbers say about a player’s abilities and contributions. The type of rebound, including whether it was contested or not, may be helpful, but without understanding a player’s role on the court at the time, it’s difficult to understand the value of the board without watching the play. Rebounds are good, that much is clear, but for individual players it’s too big of a category to be a meaningful metric.

We know that rebounding is important. It’s one of the four factors, the simplest statistical predictor of team success. Using Dean Oliver’s original weights (shooting = 10, turnovers = 5-6, rebounding = 4-5, and free throw rate = 2-3), the four factors were almost 96% accurate in predicting team performance over the last 3 years (data from BasketballReference.com)...

Even without the other three factors, though, team rebounding % has a positive correlation with winning.

Teams that tend to outscore their opponents also tend to rebound well. Put another way, better team rebounding is either a cause, a symptom, or a by-product of being a good basketball team. The relationship is such that a 1% increase in rebound % is generally equivalent to a 1 - 2 point increase in team net rating. The best 3 teams from each of the last 3 years have an average net rating of +2.3, which amounts to about 49 wins, or 8 games over .500 each year.

Individual rebounding, however, has a much less direct relationship to any other statistical predictor of individual or team success. Even the very best rebounders, by per game stats, see very little positive return in terms of team wins, especially when compared with the rest of the box score.... The difference between the value of rebounds and the other box score stats is most likely attributable to the difference in value between different types of rebounds. Two points is always two points, but one rebound can lead directly to a bucket, or be almost worthless. It’s easier to understand how different one rebound can be from another when you see it.

This is a contested offensive rebound that creates a high value opportunity, with LaMarcus drawing a foul just before the shot that would’ve been an and-1.

https://streamable.com/ejri3

This is a common defensive rebound with no opponents in the vicinity. The play, the personnel, the situation, and/or the scheme have combined to produce a scenario where the defensive team is getting the rebound with little or no resistance. On this play, LaMarcus grabs the board, but either Danny or Rudy could have easily secured it. Only Patty was actually doing work by half-heartedly boxing out Clint Capela, who is really only half-heartedly going after the ball.

https://streamable.com/9iy2e

This one, off a missed free throw, is essentially meaningless. The player who happens to be standing in that spot gets the board, in this case, Pau. Each of these plays counts as one rebound, but the value of each is vastly different.

https://streamable.com/ykjow

Using stats from NBA.com, we can get a slightly better look at the types of rebound a player gets. They provide information on how many contested rebounds a player grabs, broken down into both offensive and defensive. Here are the league leaders in total contested rebounds, contested offensive rebounds, and contested defensive rebounds from the 2017-2018 season.

If you looked closely at the results, you’ve probably already spotted the problem. Being good at grabbing contested rebounds doesn’t appear to be any more predictive of team success than rebounding in general. In fact, if we use the same expedient approach we used on traditional box score statistics (W-L record for top 3 in the league for the last 3 seasons) we get essentially the same results. The best players in the league at grabbing contested rebounds were only 2.5 games over .500 per season, just a little better than total rebounds.

That leads us back to team rebounding. It’s the only aspect of rebounding with a good correlation to team success, which means finding a way to measure a player’s impact on team rebounding, without caring how many rebounds they actually pull down, could be meaningful. Fortunately, NBA.com’s impact tool provides the data to determine how a team’s offensive, defensive, and overall rebound percentages change with a player on and off the court, though the data only goes back to 2015-16. You can also find much of this information with pbpstats.com’s team on/off tool, with the added advantage that you can go all the way back to 2001-02.

The data is here (*players who were traded during the season are excluded). It is essentially +/- information for how a team rebounds with and without each player on the court, and as such, is subject to all the usual disclaimers about lineups and rotations (e.g. if your backup is bad, you will look very good, regardless of whether you actually are). You can see it plotted, along with traditional per game rebounding numbers and individual rebounding % against individual net rating here. There’s a lot of interesting information in the data, like Steven Adams’ impact on the rebounding #s of every member of the Thunder. If you share meaningful minutes with Adams, you’re among the league leaders in effect on team rebounding %. If you don’t, you’re at the bottom...

Looking at the whole league for last season, there is a positive correlation between individual impact on team rebounding and individual net rating.

You can see how broad the distribution is. It’s not a strong correlation, but every 1% increase in impact on team rebounding is generally equivalent to a 1 point increase in individual net rating. It’s a better fit than either rebounds per game or individual rebound %, and much better than either offensive or defensive rebounds alone.

It’s important to note that this holds true even when we control for position by dividing into guards, wings, and bigs. This is surprising, particularly in the case of guards, because a common argument for guard rebounding is that it enables teams to get into transition faster. While it may be true in certain cases, it doesn’t appear to hold across the board. Using guard rebounding from BasketballReference.com, and team transition data from NBA.com, aggregated guard defensive rebounding by team wasn’t related to transition success in the 2017-18 season in terms of total opportunities, points per possession in transition, or total transition points.

With little direct relationship to team success, either in terms of team rebounding or creating more valuable opportunities, per game rebounding numbers and individual rebound percentages should be largely irrelevant in the evaluation of players and their value. How the team rebounds when that player is on the floor is far more important.

Which brings us back to where we started. If you don’t rebound well, your team is likely to lose, but having one of the best rebounders in the league on your team doesn’t mean your team will rebound well or win. Offensive rebounds, contested rebounds, and especially contested offensive rebounds are clearly valuable, but players who excel at grabbing them don’t necessarily win any more games than those who don’t. Even measuring a player’s impact on the team’s rebounding percentages offers less insight into team success than simple per game stats for assists, blocks, or steals.

After all that, if you’re still into double-doubles, or lamenting Aldridge’s rebounding #s, it’s time to rethink your position...

In that respect, the team is in good position to get after one component of the four factors. If you played around with the tool above, though, you know that rebounding isn’t nearly as important as shooting and turnovers...

Contested offensive rebounds are exponentially valuable. Uncontested defensive rebounds have little value. Defensive rebounds off missed free throws have almost no value. Team rebounding is more valuable than individual rebounding. Guard rebounding has no real relationship with success in transition offense.

http://grantland.com/the-triangle/party-crashers-debunking-the-myths-of-offensive-rebounding-and-transition-defense/

Party Crashers: Debunking the Myths of Offensive Rebounding and Transition Defense
September 12, 2013
by Zach Lowe

...Doc Rivers has been perhaps the loudest coach in proclaiming the irrelevancy of the offensive glass:

“So, you’re a big believer in offensive rebounds I think; I’m not. Listen, like I said, you can pick on that all I want. That is a number I rarely look at, is offensive rebounds. Statistically it holds up. I can tell you, you don’t offensive rebound, you stop transition, you win more games than when you get offensive rebounds. I can guarantee you that on those stats.”

But he’s far from the only one. The Spurs under Gregg Popovich have long punted on offensive rebounding out of the same belief, and several of the most successful teams in recent NBA history — Rivers’s Celtics, Stan Van Gundy’s Magic, Mike Brown’s Cavaliers (to a lesser extent), the current Miami Heat — have been happy at the bottom of the league’s offensive rebounding ranks. League-wide, offensive rebounding rate has been on a prolonged drop. “As a coach, you look at what is most important to winning and construct a game plan around that,” says Jeff Van Gundy. “And offensive rebounding just doesn’t seem to have a correlation with winning big.”

There are two connected assumptions here:

1. Crashing the boards means sacrificing transition defense.

2. Offensive rebounding doesn’t really matter.

The Pacers are basically spitting in the faces of both of those assumptions. And in doing so, they are hinting at a burbling reconsideration around the league of the relative importance of offensive rebounding in general. “We understand it’s extremely difficult to be good at both,” says Frank Vogel, the Pacers’ head coach. “But I think you have to try to be good at both. There are a lot of opportunities to explore.”

Indiana last season allowed exactly 10 fast-break points per game, the lowest figure in the league in five years, per NBA.com. The stat-tracking service Synergy Sports classified about 11.5 percent of Pacers opponent possessions as “transition” chances — also the lowest mark in the league. The Pacers allowed just 1.03 points per possession on those transition chances. Guess where that mark ranked league-wide?

Oh, you prefer the transition-points-allowed numbers at Team Rankings, which uses its own formula? The Pacers blew the league away by that standard, too...

The Pacers obviously aren’t worried. When Brian Shaw left to coach the Nuggets, Indiana hired Nate McMillan to work as Vogel’s lead assistant. McMillan’s Portland teams were the proto-Pacers — monsters on the offensive glass and in fast-break prevention. Both coaches have strict rules in place designed to ensure three players chase after every miss, they say.

If both big men are in the paint, Vogel expects them to pursue offensive rebounds. The third player will be a wing, typically the guy hanging out on the weak side along the baseline, Vogel says.

...There are sub-rules. ... Modern NBA offenses often space the floor by having a shooter in each corner, and under the Vogel-McMillan system, one of those guys is supposed to hit the glass. But that player cannot just take a straight-line path along the baseline, McMillan says. Instead, he should loop from the corner up toward the foul line when a teammate shoots, and once along that path, decide midway whether he’s got a shot at the offensive board.

Following that curl pattern ensures the player will have already started retreating back on defense in case the rebound goes elsewhere, or if the player concludes he has no chance at it, McMillan says. Scrambling along the baseline would leave that player way behind the action.

Vogel and McMillan have rarely altered these principles, not even against LeBron’s Heat or the Steve Nash–era Seven Seconds or Less Suns. Both believe having more players crashing the offensive glass might actually make their team’s transition defense better. If opponents know the Pacers are going to chase boards like maniacs, those opponents can’t start leaking out for fast breaks, the coaches say. “We always felt like if we were putting pressure on opponents to box us out,” McMillan recalls, “then they couldn’t get out and run.”

It’s tempting to look at all this and suggest coaches are leaving points on the table out of caution. That was essentially the conclusion of several MIT students who used camera-tracking data to see (among other things) how often teams had two, three, or even four players crash the offensive glass — and what happened as teams sent an extra body or two to the boards. The general conclusion the authors presented at the MIT Sloan Sports Analytics Conference in March, based on data from the 2011-12 season, was that teams could net about four extra points per game by recalibrating their philosophy toward offensive rebounding — that teams were being too cautious.

...And that’s something that might be behind the long-term decline in offensive rebounding — spacing, and the emphasis on the 3-point shot, and especially the short corner 3. If a team has all three perimeter players out there, including two in the corners, they’ve got a long way to go to get into rebounding range, and taking a few false steps toward the rim could affect transition defense. And if you’ve got a stretch power forward .. forget about it. Personnel drives spacing, and the emphasis on spacing has taken guys away from the basket. “Teams now rely on spacing so much,” McMillan says. “And you see it all the time, teams whose spacing is such that when a shot goes up, they don’t even have one person going to the boards. They are just conceding the offensive glass.”

There is a growing sense that teams have gone too far in offensive rebounding paranoia. Jeff Van Gundy wonders if this is especially true in the playoffs, when the pace slows, teams face the very best defenses, and points become more scarce. “You have to ask yourself: In the playoffs, is offensive rebounding more important?” Van Gundy says. “Because scoring is harder. And so, should we construct an offensive rebounding identity early, so that we have another weapon in the playoffs?”

And yet, the correlation between offensive rebounding and winning is still very low, according to several stats experts around the league. Is there a chicken-and-egg thing going on there? Or does offensive rebounding really not matter, as Van Gundy and other coaches have found in the historical data? After all, we’re talking about only a handful of possessions each game. Teams snag only 11 offensive rebounds per game on average, and not all of those lead to baskets or free throws. Would jacking that number up to 14 or 15 really make a difference, especially considering that the very existence of an offensive rebounding chance flows from a negative event — a miss? Maybe teams who are “good” at offensive rebounding are good because they miss a lot — because they are bad at offense.

No one is sure, not in a league where the difference between winning and losing could be a couple of bad bounces. But the idea that good offensive rebounding and good transition defense are mutually exclusive appears to be a myth....

https://www.espn.com/nba/story/_/id/14505051/transition-defense-left-offensive-rebounds-cutting-room-floor

Why are teams bored with boards?
Jan 4, 2016
Zach Lowe

Brett Brown still remembers the mantra Gregg Popovich and his staff in San Antonio recited to warn perimeter players against chasing offensive rebounds.

"We don't care if you get an offensive rebound in your entire life," Brown says, laughing. "And we'd say it to them exactly like that."

Popovich was among the first in a wave of coaches to order four or even all five players to run back on defense the moment a shot went up. Retreating prevents fast-break points and forces opposing offenses to work against both a set defense and the dwindling shot clock. That is the first step in quieting explosive opponents, and any tactic that ran counter to it -- such as having too many guys crash the offensive glass -- would be used only in tiny doses. It is almost orthodoxy in most of the NBA today: Offensive rebounding doesn't matter, especially because it threatens the integrity of your defense.

"San Antonio set the model," says Terry Stotts, the Blazers' coach. "Offensive rebounding has never been a priority for us."

Doc Rivers, Stan Van Gundy, Steve Clifford, Erik Spoelstra and Rick Carlisle are among the coaching giants who have (mostly) gone down the Pop path.

"Right now, everything is tilted toward transition defense," Brown says. "We are all sheep."

Players feel the shift too. "Years ago, every coach was looking for offensive rebounds," says Luis Scola, Toronto's starting power forward. "And now it's so different, because coaches don't want to give up transition points. That's why players stopped doing it."

....The historic drop-off goes beyond transition paranoia. Teams are playing more small ball, and asking their power forwards to shoot 3s -- slotting good rebounders 25 feet from the rim. "You're just so far away," says Kris Humphries, who barely snags offensive boards now that the Wizards have turned him into a 3-point shooter. "It's hard to run all the way in, and then run back on defense." Kevin Love, Serge Ibaka, Scola and lots of other reinvented snipers could empathize.

Smaller teams also move faster; the league's overall pace keeps jumping, and that fuels the fear that overeager offensive rebounding can turn every opposing offense into the Warriors.

The rise in 3-point attempts also has deflated offensive rebounding. More jumpers mean fewer shots at the rim -- missed bunnies that produce the most offensive rebounds, in part because the shooter is often in good position to catch his own miss. Long shots lead to long rebounds, per SportVU data, but not the sort offenses retrieve at a high rate.

... Coaches are starting to wonder whether crash-phobia has gone too far.

"It's something we're all struggling with," says Brad Stevens, the Celtics' coach. "Teams all place a large focus on defensive rebounding. If that's important, then offensive rebounding must be important, too."

The difference between rebounding 23 percent and 30 percent of your own misses -- what the league averaged not long ago -- might amount to only two or three extra possessions each night, but in a close game, that could make a huge difference.

"There isn't one coach who doesn't put a high premium on defensive rebounding," Stotts says. "But doing that, while ignoring offensive rebounding -- that's the paradox."

Says Brown, simply: "There is a huge disconnect there."

Fittingly, the very changes that appear to be phasing out offensive rebounding -- 3s and small ball -- are driving coaches to reconsider their approach to it. Kickout 3s immediately after an offensive rebound are among the very best shots in the game. Over the past two seasons, teams have shot about 39.5 percent -- well above the league average -- on 3s attempted one pass after an offensive rebound, per data from Vantage Sports supplied to ESPN.com. So far this season, teams have nailed about 39 percent of triples launched five or fewer seconds after an offensive rebound, per SportVU data provided to ESPN.com

"If you kick it out and get a 3, that has very powerful momentum," says George Karl, the Kings' coach.

"It's just so deflating to defend for 23 seconds, give up a rebound, and then have it turn into a 3," Stevens says. "It reminds you how big an impact offensive rebounds can have."

... This is one area where the clichéd conflict between analytics experts and coaches is still happening. A lot of analytics staffers have pushed coaches to get more adventurous crashing the glass, only to find that coaches can't stomach the risk. And in some cases, those coaches may be right.

At the same time, the paranoid offensive rebounding teams tend to be among the best at limiting fast-break points.

In other words: There may be real danger in banking too much on offensive rebounds. And that may be especially true for the best teams. Good teams have good offenses, and good offenses make almost half their shots. If the first shot is a decent bet to go in, perhaps the risk-reward calculus favors getting back on defense. This probably plays some role in explaining why good teams appear to avoid the offensive glass: because they're good, not because offensive rebounding is on its face a bad thing.

.. Brown is trying to teach Philly's corner shooters to loop up toward the foul line when a teammate launches a 3-pointer, just in case a long rebound happens to carom there. Both Stotts and Frank Vogel encourage the same tactic. "With everyone shooting 3s, you might be able to pick up some cheap points," Brown says.

The best modern offenses organically manufacture offensive rebounding opportunities they might be passing over now. Whip the ball side to side through two or three pick-and-rolls, and the defense will be scrambled by the time you shoot. Defenders will have rotated into mismatches, sprinted way outside to fly at shooters, or drifted into space after running around.

On pick-and-rolls, most defenses shift away from shooters on the weak side to clog up the paint. Smart cutters like Dwayne Wade slice backdoor for layups in that moment when their defender sneaks toward the ball. The same cut can put a little guy in prime offensive rebounding position; the Rockets, for instance, let Patrick Beverley skulk for these sorts of offensive rebounds. "I respect the counterargument about getting back on defense," says Daryl Morey, the Houston GM. "But when you have Patrick Beverley, it would be a mistake not to use his offensive rebounding."

No one knows the right balance, only that it varies by team, opponent and specific personnel. The ideal scenario is probably to have one big guy so unstoppable on the glass, he single-handedly props up his team's offensive rebounding -- leaving four teammates to run back on defense. This is the Andre Drummond archetype.

"That is really the best of both worlds," Van Gundy says.

https://clutchpoints.com/the-lost-art-of-the-offensive-rebound-an-analysis-of-causes-and-implications/

80 percent of all NBA rebounds happened within eight feet of the hoop. 56 percent of missed corner 3s end up rebounded on the weak side.

Among 51 qualified centers and forwards who averaged at least five field goal attempts per game, 70 percent recorded 10 or more 3-point attempts this season. Rewinding back to the 2007-08 season, that number dips to just 9 out of 44 eligible players, i.e. ~20 percent with a neglectable number of attempts from beyond the arc.

The prototypical big man of the new era constantly moves, sets screens and pops to the three-point line as a triple threat, or simply roams the perimeter, opening up space for slashing guards, prepared to shoot the ball the moment the defense collapses to protect the rim. Under those circumstances, securing a position in the painted area quickly started moving towards the low-end of the list of priorities.

Lack of correlation with winning

Here is where the past ten NBA Champions ranked in terms of offensive rebounds over the course of the regular season:

"I want it (rebounds) more. That's all it really is."
- Andre Drummond

"No rebounds, no rings."
- Pat Riley

"I want to do for rebounds what Michael Jordan did for dunks."
- Dennis Rodman

Chandler wrote:

not sure i agree with some of the stats. team that rebounds better will either limit/reduce the other teams shot attempts and/or increase their own

if the stat is just a count it can be misleading. For example, you won't get a lot of defensive rebounds if the other team scores on every shot-- in fact you'll get 0

similarly you won't get a lot of offensive rebounds if you score on every possession -- again you'll get 0

so a better stat normalizes based on opportunities.

there is also the lost art of the team rebound. Long ago the celtics were masters, some number of players were responsible for simply boxing out their man. 1 or 2 others were actually responsible for the rebound -- those who were expected to have a significant mismatch

When Larry Bird was a player and coach he liked guards who could rebound. I think that is all the more prescient in today's NBA with more 3 point attempts and long rebounds which can transition into fast breaks much easier (often forgotten downside of launching 3s)