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February 16, 2012
Getting Back
Quantifying Transition Defense

by Kevin Pelton

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For today's column, we've brought in special guest Avery Johnson to deliver the introduction. You see, we're talking about one of Johnson's favorite topics: transition defense, or as the coach of the New Jersey Nets pronounces it in his unique Louisiana patois, "tran-zee-shun dee-fense."

Despite all the time coaches spend thinking about transition defense, the concept has received precious little attention from statistical analysts. In large part, transition defense defies easy quantification. For as long as I can remember, the NBA has included fast-break points in its official box scores, but over the course of the season the stat is difficult to find and challenging to interpret. Simple fast-break points don't factor in opportunities or efficiency.

Fortunately, transition defense is one of the places where the new treasure trove of data provided by MySynergySports.com can help. Synergy marks plays as in transition, which allows us to consider both how often teams give up transition opportunities and how effective their opponents are at converting them.

This presents a different question: How can we combine these two numbers into one overall measure of transition defense? To do so, I brought back the average value of any play, transition or not (about .9 points). The difference between this and a team's points allowed per transition play represents the points lost per transition opportunity. Then we can multiply that by percentage of plays in transition to find the total points lost to transition. The lower this score, the better the transition defense. Here are the rankings, through last Tuesday when I compiled the numbers:

Team    %Ply      PPP     Tran
------------------------------
CLE     .112     0.97     0.76
PHI     .093     1.01     1.00
MIA     .129     0.99     1.14
TOR     .117     1.08     2.08
ORL     .107     1.10     2.12
ATL     .123     1.08     2.19
PHX     .099     1.14     2.36
UTA     .120     1.10     2.38
DAL     .124     1.10     2.46
CHI     .115     1.12     2.51

Team    %Ply      PPP     Tran
------------------------------
IND     .127     1.10     2.51
SAS     .117     1.12     2.55
HOU     .124     1.11     2.58
POR     .149     1.08     2.65
MIL     .135     1.11     2.81
GSW     .136     1.11     2.83
MEM     .139     1.11     2.89
NYK     .128     1.13     2.92
LAL     .115     1.16     2.97
SAC     .150     1.10     2.97

Team    %Ply      PPP     Tran
------------------------------
OKC     .120     1.16     3.10
DEN     .125     1.15     3.10
BOS     .100     1.22     3.18
DET     .132     1.15     3.27
MIN     .128     1.16     3.30
CHA     .140     1.14     3.33
LAC     .130     1.16     3.35
WAS     .136     1.15     3.37
NOH     .125     1.22     3.98
NJN     .132     1.22     4.20

The transition defense metric can be interpreted as the number of points lost to transition opportunities per 100 overall plays, while the points per play uses transition plays at the denominator.

There are a few things worth considering here. First, as you might guess, transition opportunities are much more effective than half-court situations. Just two teams--the Cleveland Cavaliers and the Miami Heat--allow less than a point per play in transition. The worst teams in the league are allowing the equivalent of 60 percent shooting.

Which is more important, limiting transition opportunities or cutting down on points scored per transition play? In practice, the points per play ends up making up more of the transition points lost. There's more variability in points allowed than opportunities. Teams only have so much control over either factor. Turnovers and situations where opponents can cherry pick are going to create transition points no matter how sharp the focus on getting back defensively. Still, there are real differences between teams.

In general, the results make sense. I think the most surprising ranking is Boston in the league's bottom 10. Doc Rivers is one of the coaches I would expect to place the most emphasis on transition D. The Celtics have in fact allowed very few transition opportunities, but have been getting beaten in those chances as badly as any team in the league. Maybe that will even out over time.

I am not at all surprised the Philadelphia 76ers have allowed fewer transition plays than any team in the league. Getting back is a key part of Doug Collins' defensive emphasis in Philadelphia, which has paid off handsomely. Most of the other coaches in the top five are known for their focus on defense. The possible exception is Byron Scott, who has always emphasized defense, but with mixed results--this year's Cavaliers rank 20th in overall Defensive Rating, but tops in transition.

Cleveland aside, better defensive teams usually have superior transition defense. There's overlap between five of the top 10 teams in this metric and Defensive Rating, while none of the bottom five teams in transition defense rank better than 24th overall on defense.

The original impetus for this research was to answer a question we tackled on last week's edition of the Mythbusters podcast I'm doing on the Utah Jazz website with radio play-by-play broadcaster David Locke: do offensive rebounds hurt defense? The conventional wisdom amongst most defensive-minded coaches is that sending players to the offensive glass is a net negative because of the transition opportunities it allows at the other end.

Indeed, there is a negative correlation between a team's offensive rebound rate and it's transition defense score, but the relationship is far from perfect. For example, the Cavaliers also rank third in the NBA in offensive rebounding. The Utah Jazz and Chicago Bulls have also found ways to achieve strong marks in both offensive rebounding and transition defense. As a result, when I looked at overall Defensive Rating and offensive rebounding, I found no relationship between the two.

So the importance of transition defense might be slightly overstated by coaches. If so, don't tell Avery Johnson. He's too busy yelling at his team, currently last in the league in tranzeeshun defense, to get back downcourt.

Kevin Pelton is an author of Basketball Prospectus. You can contact Kevin by clicking here or click here to see Kevin's other articles.

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