Does offensive rebounding affect transition defense?

Dylan Burkhardt
on
Michigan 61, Syracuse 56 extra-27John Beilein teams have never been renowned for their ability to crash the offensive glass. Last year the Wolverines jumped 100 spots in offensive rebounding but still ranked just 139th in the country and 8th in the Big Ten.

Beilein has never been shy to share his philosophies on the matter. He would rather play steady transition defense than crash the offensive glass for an extra possession. That logic has largely been driven by the fact that Beilein has rarely had the personnel to justify crashing the offensive boards.

Michigan’s head coach is not unique in his thinking but Grantland.com’s Zach Lowe argues that he might be incorrect in his recent story ‘Party Crashers: Debunking the Myths of Offensive Rebounding and Transition Defense’. Lowe notes Gregg Popovich, Doc Divers, Mike Brown and Stan Van Gundy as highly regarded NBA coaches that share the same philosophy.

Lowe concludes that great offensive rebounding teams can be good, bad or mediocre transition defenses. There’s no correlation between the two statistics. Lowe’s study focuses on the NBA, mostly the Indiana Pacers and his results prove true in the college game as well. Picking up where Lowe left off, I crunched some numbers to look for a correlation between offensive rebounding and transition defense at the collegiate level.

I pulled every Division I team’s offensive rebounding percentage, points per transition possession allowed and percentage of transition possessions allowed to look for any correlation. Those three metrics give us: how effective teams are on the offensive glass, how effective they are at stopping transition offense and how often they give up transition possessions.

The first scatterplot below shows the percentage of transition possessions allowed against offensive rebounding for every Division I team last season. This graph looks for some correlation between how many fastbreak possessions a team allows and their offensive rebounding effectiveness.

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The next scatterplot compares points per transition possession allowed against offensive rebounding percentage for every Division I team last season.

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Those charts tell us that there’s very little, if any, correlation between offensive rebounding productivity and transition defense (both quantity and effectiveness). There’s slightly more correlation in the first graph which makes sense. Conventional wisdom is that the more often you crash the glass, the more often your opponent will fast break.

The next graph, transition effectiveness, actually shows a very slight negative correlation, meaning that the better offensive rebounding teams actually do a better job of defending transition opportunities. This somewhat makes sense as these teams could have the best athletes, but the R-squared value of less than .03 tells us that this is essentially a random sampling of data.

The major caveat with this dataset lies on the offensive rebounding side of the equation. Offensive rebounding percentage measures how effective a team is at crashing the glass, it doesn’t say for certain how aggressive they are. One team could crash hard but not come up with many offensive rebounds, another team could send just one player but he grabs a team’s worth of offensive rebounds.

Studying offensive rebounding aggressiveness would require extensive film analysis, something this study did for the NBA. However, it’s a reasonably safe assumption to conclude that offensive rebounding percentage and offensive rebounding aggressiveness are fairly correlated.

The numbers very clearly support Lowe’s argument. There’s no correlation between offensive rebounding and transition defense on a broad level.

Rebounding, transition and Michigan

While there’s no correlation on a national scale, Michigan’s 2012-13 team was its best offensive rebounding team in the last three years. It was also Beilein’s worst transition defense team of the last three seasons.

The Wolverines allowed opponents to fast break on 13.4% of their offensive possessions – the sixth most allowed by any Big Ten school over the last three seasons. In the two years prior, Michigan allowed opponent transition possessions on 10.3% and 9.9% of their defensive trips – the two lowest percentages of any Big Ten school over the last three seasons.

Year Transition Poss% Transition PPP OR %
2012-13 13.40% 0.987 32.5
2011-12 10.30% 0.972 25.8
2010-11 9.90% 1.008 21.5

So the Wolverines went from being one of the very worst offensive rebounding teams and the very best transition defense to a decent offensive rebounding team and an awful transition defense.

Michigan’s numbers over the last three seasons demonstrate the very trend that this post set out to disprove. So what gives?

There are two probable explanations for this phenomenon:

  1. Michigan had an extraordinarily young and athletic team. The youth led to worse transition defense while the athleticism led to improved offensive rebounding.
  2. Michigan was had to be significantly more aggressive in its offensive rebounding approach to reach that improvement, and it paid the price for it with its transition defense.

I tend to side with number one. Michigan had a young team and young teams can lack the discipline to play great transition defense.

If number two were the case, it was a mistake in philosophy. The numbers show that the gain the Wolverines saw on the offensive glass didn’t match its loss in transition defense.

Year OReb Poss/Gm OReb Pts/Gm Trans Poss/Gm Allowed Trans Pts/Gm Allowed
2012-13 5.1 5.3 9.9 9.8
2011-12 3.4 3.7 7.2 7
2010-11 4.2 4.3 7.1 7.1

Michigan surrendered just under three points per game more in transition defense last season compared to the two seasons before but only saw a scoring increase of roughly half of that in second chance points.

Next Year

The good news is that the Wolverines should be able to improve their transition defense and their offensive rebounding without any drastic change in strategy. John Beilein has the league’s best offensive rebounder in his back pocket: Mitch McGary. Michigan doesn’t have to send more players to the offensive glass, it just has to send McGary. 

McGary’s offensive rebounding rate of 16% ranked 10th best in the country and was best in the Big Ten. His production regressed to a degree in league play but with the opportunity to be a full time starter, his ability to impact Michigan’s overall offensive rebounding effort will increase significantly. With McGary in the lineup full time, Michigan could move into the top-half of the Big Ten in offensive rebounding for the first time since 2008.

The net-benefit of sending more players to the offensive glass might be limited unless the Wolverines move to a two big lineup. With McGary at the four and Morgan or Horford at the five, the intrigue of crashing the glass becomes greater. Morgan and Horford can both hold their own on the offensive glass and make an impact.

With McGary at the five, there isn’t really anyone else to send. Glenn Robinson III is a terrific athlete but he doesn’t necessarily have the temperament (or production) to justify crashing the glass every possession. Nik Stauskas grabbed 20 offensive rebounds total in his freshmen season and Caris LeVert, Zak Irvin or Derrick Walton aren’t going to make a great impact on the glass.

Michigan’s guards and wings need to figure out a way to fix the other side of the equation and shore up Michigan’s defense. Having the most efficient offense in the country last season masked a lot of problems but without Trey Burke and Tim Hardaway Jr. and with an extraordinarily young backcourt, the Wolverines can’t afford to do such a poor job of defending transition offense again this season.

  • Mattski

    And McGary is a great outlet passer, another critical factor; obviously having the right guys crash the boards is critical. (One thinks of the burly forward or center who rips down the board and flails with his elbows to maintain it; meanwhile, everyone is halfway back upcourt.)

    A fine and nuanced analysis. In the end, I think, a coach has to play to his team’s strengths. If your team shoots a high percentage and is small, Beilein’s traditional approach makes plenty of sense. Work for a really good shot and put it in the first time.

    • AADave

      Great point about having the “right guys” crash the boards. Ideally, you’d have somebody like GR III running the court as a target for the outlet pass rather than crashing the boards himself.

      • http://www.umhoops.com/ Dylan Burkhardt

        You guys are flipping things on me talking about outlet passing. Offensive rebounding is the focus here.

        • geoffclarke

          I haven’t watched the tape, but if we could cut down on McGary getting the offensive rebound and then outletting to the opponent’s fast break, that would probably help.

        • Mattski

          My bad!

        • chazer

          Hey Dylan, take no offense…were just jazzed for the season!! I always wondered what impact Trey had going to the rack and falling so often on the transition D….I know its not OR related but another variable to cloud last years numbers…excellent work, maybe raised more questions than answers given all the variables.
          Always liked playing Football….but loved playing hoops!

  • Chazer

    Well done Dylan! This is always a tough analysis given the variables of who is on the floor and your competition. If I’m not mistaken, Novak had to play the 4 spot at times so certainly getting back was crutial when he played vs crashing.

    Also, not only was the transition defense weak last year but it seemed the FRESH struggled as a team last year on D. I will say this team seemed to play better team defense in the tournament vs. B1G play. I expect it will be better this year and I’m hoping Walton and Irvin catch up defensively. Always enjoy your hard work and effort, good job!

    I still beilieve that Beilein’s team are well prepared to play tournament ball….they can, run, shoot and score with dicipline! Low turnovers and improved defense this year will make Blue a tough out! Can’t wait….Go Blue!

  • UMHoopsFan

    One current that runs through this but can get muddled is that “crashing the glass” might not have much effect on how many offensive rebounds you get. A team with one or two good offensive rebounders might get a lot of offensive rebounds even if it sends two guys back with a third to follow quickly. Conversely, if Michigan had been sending Novak, a frosh THJr, and Douglass hard to the glass every year in 2010, they still might not have corralled a ton of offensive rebounds. As a team, you want to get as many offensive rebounds as you can while giving up as few transition opportunities as you can. Now, giving Brendan Dawson a little more freedom to crash the glass than Stauskas probably makes sense — but, you want to teach both how to rebound effectively, how to get in the way of outlet passes or slow up dribblers, how to get back quickly, etc.
    My takeaway is that there may be less correlation than some people tend to think, perhaps including Popovich and Beilein and co., but this may also be a case where looking at things statistically can also lead to a wrong conclusion. In the end, teams with particular personnel might want to focus on crashing the glass vs. transition defense, but all teams shouldn’t necessarily crash the glass all the time.
    Like many things, it also might matter more against certain opponents than others.

    • http://www.umhoops.com/ Dylan Burkhardt

      Yep. I tried to note this in the post after the graphs. That’s the problem with using offensive rebounding percentage as the data point.

      • UMHoopsFan

        Yeah, but I also see why you would use that number. What other number are you going to plug in? If you could get a number on players within 10 (or whatever) feet of the basket that might be interesting, but that’s hard to come by.
        One thing it does do is point out that a lack of ORbs might be best understood as largely lacking good ORebounders as opposed to just a philosophical thing. I also wonder how the kind of shot you’re taking matters — e.g., if you shoot a lot of 3s vs 2s, jumpers vs. post-ups, etc.
        Thanks for the interesting post.

  • mikey_mac

    Great post. I love seeing the numbers crunched like this. I think UM’s regression in transition defense is likely similar to its regression in half-court defense as well. Would like to see a +/- PPP in half-court and transition situations, for 2013 compared to 2011-2012. UM had a very solid defensive team overall the previous couple seasons, that simply lacked the size to do anything on the offensive boards. Last year, that was flipped — enough size to do some damage on the boards, but a lot of inexperience and “offensive-minded” play.

    • http://www.umhoops.com/ Dylan Burkhardt

      Halfcourt Defense (PPP)
      2010-11 0.854
      2011-12 0.863
      2012-13 0.821

      Those are season long numbers. Michigan was a better defensive team overall last season, but worse in the Big Ten.

      • mikey_mac

        Wow, much better than I thought last year. I guess my recollection of their defensive effectiveness was really jaded by some of their B1G performances.

    • mazs

      A faster pace with higher scoring games does not necessarily mean the defense regressed as noted by Dylan here.

      Also, the decision to crash-the-glass (like pressing) and risk more transition baskets is acceptable for some teams, not Michigan usually, so long as it creates the game tempo that team wants—VCU would be one such example, I suspect.

  • geoffclarke

    There are a couple types of defensive transition – (1) those started with a rebound and (2) those started with a turnover. Do you think the graphs would change much if you only focused on defensive transition started with the rebound? It seems that would be the accurate correlation.

    Also, if you combine (multiply?) the transition % with the transition PPP, would the resulting “line” become more horizontal, seemingly even more random?

    By the way, love posts like this.

    • James

      I like the post too, but it’s not a very robust analysis if you ignore turnovers. The “correlation may not equal causation” when you ignore such relevant parameters.

    • mikey_mac

      UM cut their TO% by like 2.5% last year compared to 2011-12, and by 1.5% compared to 2010-11, so it would seem likely that a much higher percentage of transition opps for the opponent were started off rebounds than in previous years.

      • http://www.umhoops.com/ Dylan Burkhardt

        Good points. Should have tried to incorporate TO% into the equation… Would have to play with the numbers. There’s also no “live ball” turnovers stat so that can also be a deceiving metric.

        However, Michigan routinely turns the ball over less than just about anyone in the country and still did a very bad job in transition defense this year.

        No stats are perfect, this post certainly isn’t, but it has at least generated some good discussion.

  • Kenny

    All good coaches would do their own cost-benefit analysis based on the players he has, and the opponent, and adjust how aggressive he wants his players to crash the offensive board, to reach an equilibrium. If you do not have good rebounders and the opponent is a good transition team, then it is a no brainer. The decision is also easy against a bad transition team when you have good rebounders. It would be silly for Beilein or any other coaches not going after offensive rebounder in the latter situation.

    I don’t know how Lowe has do his analysis, but only meaningful analysis I can see is to use NBA playoffs when two teams play multiple times in less than two weeks largely having the same personnel, and track how offensive rebounding relates the effectiveness of transition defense. And the transition defense should not include those coming from turn-overs.