# Stats Analysis: Defensive Efficiency

The Bootleg's Basketball Stats Analyst Cameron Tana follows up last week's fascinating column with his analysis of defensive efficiency. Cameron spent two years broadcasting Stanford men's basketball games, the first as Dave Flemming's color commentator in 1996-97 and the second as play-by-play announcer in 1997-98. A serious stats man, Cameron has done NBA game charting for www.82games.com

Stats Analysis: Defensive Efficiency

The first article (link) in this series introduced possession-based efficiency statistics. These statistics were illustrated by looking at the offensive ratings of Stanford men's basketball teams over the last 11 years. Today, we'll look at the team defense over the 13 of the last 14 seasons (we'll start with these seasons and update this article when we can unpack our stats going back to 1986-87, the first season with the three-pointer).

As discussed in the first article, the building block for evaluating offensive and defensive efficiency is to adjust by possessions or pace of play. Offensive rating is "points scored per 100 possessions" and defensive rating is "points allowed per 100 possessions." Because number of possessions isn't an official statistic, we have to estimate it from the box score. We will use the same formula Ken Pomeroy uses to show NCAA efficiency statistics at kenpom.com:

Possessions: Field Goals Attempted - Offensive Rebounds + Turnovers + 0.475 x Free Throws Attempted

With this basic formula in hand, let's rank the teams by defensive rating (points allowed per 100 possessions) for the last 11 years.

 Season Possessions Per Game Defensive Rating Effective FG% Defensive Rebound Rate Turnover Rate Free Throw Rate 2000 70.3 84.8 39.6 71.0 19.6 16.1 2004 67.7 89.8 44.0 70.5 21.7 18.6 1999 67.5 90.1 42.3 70.2 19.2 18.1 1997 74.3 93.0 46.6 69.6 21.1 19.9 1996 71.3 93.6 47.0 68.9 21.1 17.6 2001 69.6 94.0 47.4 72.2 20.6 15.8 1994 75.7 94.5 47.3 69.1 21.5 21.3 1998 72.2 94.7 46.7 73.3 18.5 18.7 2003 68.4 98.3 45.6 68.2 18.7 21.1 2007 67.7 99.1 46.2 70.3 17.3 21.1 2006 65.8 99.2 47.2 67.9 19.9 20.8 2005 69.3 99.4 47.9 65.6 21.3 19.6 2002 72.4 100.5 47.3 70.9 17.0 21.5

The 2000 team that was the first to earn a #1 seed in the NCAA tournament but lost to North Carolina in the second round is easily the most efficient defensive team of the last fourteen years. This team featured a formidable frontline rotation in Mark Madsen, Jarron Collins, and Jason Collins. The backcourt was Mike McDonald and David Moseley. Freshman Casey Jacobsen started midway through the year over Ryan Mendez. There are four factors making up defensive efficiency that mirror the offensive factors. Here are four defensive factors in approximate descending order of importance.

Effective FG% = (Opponents Field Goals Made + 0.5 x Opponents 3 Pointers Made)/Opponents Field Goals Attempted

Forcing missed shots is easily the most important factor in defense. Even accounting for the additional point gained by making a three pointer, the 2000 team kept opponents effective FG% under 40%.

Defensive Rebound Rate%= Defensive Rebounds/(Defensive Rebounds + Opponents' Offensive Rebounds)

This factor divides defensive rebounds by the number of defensive rebounding opportunities. The often-used rebounding totals and rebounding margins are less useful because they depend on the number of shots missed. If your team forces a lot of missed shots, it's more likely they will get more defensive rebounds. The other thing rebounding rates do is separate what happens at the offensive and defensive ends of the floor. Offensive rebounds should be compared to opponents' defensive rebounds. Defensive rebounds should be compared to opponents' offensive rebounds. The 2000 team was a solid defensive rebounding team, but the highest-rated defensive rebounding team was the 1998 Final Four team with Tim Young, Mark Madsen, and a big small forward in Peter Sauer. We have not collected all of the statistics for the Adam Keefe years yet, but in 1990, his sophomore year, the defensive rebound rate of 67.8% would not rank highly on this list.

Turnover Rate = Opponents Turnovers/100 Possessions

This factor measures the percentage of opponents' possessions stopped with turnovers. This is not typically a big part of the Stanford defense. The second-most efficient defensive rating was held by the 2004 team that was undefeated much of the year. This team was the best in the last eleven years in defensive turnover rate, but the national ranking was still only 158th according to kenpom.com. Although Chris Hernandez led the team in steals, I tracked individual defensive statistics in 17 games that year and it was the Justin Davis/Nick Robinson rotation at power forward that was most likely to force turnovers. Still, anchored by Josh Childress and Rob Little, this team's strengths were effective field goal defense (sixth in the nation) and defensive rebounding rate (11th in the nation).

It is also notable that the 1994, 1996, and 1997 seasons rank highly in this category. These are three of the seasons in the Brevin Knight era. Knight is Stanford's career steals leader. We have not yet processed the final statistics from Knight's sophomore year.

Free Throw Rate = Opponents Free Throws Made/100 Possessions

This factor measures the propensity of the defense to foul and give up points from the line. The statistics on kenpom.com use opponents' free throw attempts in the numerator using the logic that defenses can't guard the free throw. However, defensive strategy can dictate whom to foul (e.g. "Hack-a-Shaq") so I'll use 'makes' here. The 2000 and 2001 teams were tops in this category.

It is interesting what a difference a year can make. Both 2000 and 2001 teams were excellent teams that played at about the same tempo. However, the 2000 team was best at defense and the 2001 team best at offense. Losing David Moseley and Mark Madsen and pairing Casey Jacobsen and Ryan Mendez on the wings worsened the defense by nine points per 100 possessions. The 2001 team made up for most of that by improving the offense by over seven points per 100 possessions.

Unlike the offense's consistency, Casey Jacobsen's teams are all over the map on defense. His junior year had the worst defensive rating on the list. Fellow junior Curtis Borchardt may have blocked nearly three shots per game, but the team's overall effective field goal percentage was on the high end. Even for a Stanford team, this group had a very low defensive turnover rate.

Also grouped near the bottom of the table are the most recent three years under Coach Trent Johnson. Like offense, it is rather discouraging to see what similar ratings his three teams have had. At least, the core of this year's team showed an improvement in defensive rating last year. They did a better job defending shots (ranked 38th nationally according to kenpom.com) and rebounding misses (ranked 13th nationally). In a mirror image of the offense, the "caused" turnover rate was extremely low (ranked 334th out of 336 in Division I) and the free throw rate was high (ranked 150th). I'd expect at least the latter to change as the young players learn what they can get away with. The team is going to have to continue to improve field goal defense and force turnovers at a more respectable rate if they are going to take a step forward this year.

Next, we'll build on the fundamentals introduced in these first two articles, and look at individual player offensive efficiencies. The first example of that will be a look at the year-by-year offensive efficiencies of Stanford point guards and how current point guard Mitch Johnson compares to previous 1s after their first two seasons on the Farm.

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