Franalysis: A Look At Luka Garza's Improved Defense

By houksyndrome on March 24, 2020 at 10:01 am
block luka block
© Jeffrey Becker-USA TODAY Sports

The story of the 2019-20 Iowa Men’s Basketball Season was, without question, Luka Garza.  Garza, who could well become the first Hawkeye Men’s basketball player to win the Naismith Trophy, is widely renowned for his offensive prowess.  That renownededness* is well deserved.  A catalog of Garza’s offensive exploits is not the purpose of this article so I’ll just throw a few of them out there:  23.9 PPG with a 58% effective FG%, Iowa was the 5th best offense in the country and calling Garza the focal point of that offense seems like a gross understatement.  By offensive criteria, Garza is a very strong Naismith/Wooden contender.  But this article isn’t about his offense, it is about his defense, which, while not elite, was also dramatically improved this season compared to his first two seasons at Iowa.

*Due to my anxiety over the COVID-19 pandemic, I have started to make up my own words as a coping mechanism.

Let’s start with my own personal observations and then get into some statistics later on.  In my opinion, the defensive impact of a center is largely determined by his ability to do three things:  (1) protect the rim without fouling, (2) control the defensive glass, and (3) defend guards on the perimeter after being switched, as often occurs when defending the high ball screen (aka, “pick and roll/pop”).  It is very hard to do all three of these things at an elite level.  In fact, it is so hard that if you are able to do them, you’ll probably be able to play in the NBA even if you have virtually no offensive skills.

It was obvious from the beginning of his Iowa career that Garza was going to be a useful offensive player for us.  His shooting touch and post moves were good for an incoming freshman.  His defense, though, not so much.  I was impressed with his rebounding (he's always had one hell of a motor), but he didn’t block a lot of shots, he fouled a lot (more on that below), and he was often a complete mess when trying to defend on the perimeter.  This was true when hedging on ball screens and also when trying to close out on three point shooters when Iowa played zone defense.  Apologies for bringing up the 2017-18 season, but does anyone else vividly remember team after team torching Iowa on corner threes as Garza attempted to make that extremely long and difficult close out?  It will be seared into my memory until the mercy of death takes it away.  Many of these problems were still there in the 2018-19 season, as Garza still wasn’t much of a shot blocking presence and still struggled when asked to defend on the perimeter.  Simply, Garza isn’t gifted with great quickness or explosiveness so defense will always be the question mark for him.  Coming into this season, I was resigned to the idea that Garza’s offensive contributions would always be negated, to some degree, by poor defense.

This season, however, Luka Garza was a new man.  After going through a Rocky-esque off-season workout regime, Garza was much stronger, extremely well-conditioned, and a more mobile and explosive athlete.  As a result, his defense was considerably better, particularly his rim protection (more on that later).  His perimeter defense looked dramatically better to my eye as well, even if it was still not great.  Overall, his off-season defensive improvement has given me hope that, if he stays at Iowa for the 2020-21 season, he could make even more improvement on that end of the floor, which is critical for Iowa to become Big Ten contenders.  Hopefully he feels the same way and returns next year with a mind to prove that he can be an NBA-level defender, which is probably the deciding factor in determining what kind of a chance he gets with the NBA.  It would also help if Iowa would adopt a defensive strategy that minimizes the amount of perimeter defense that Garza has to play.

There is also strong statistical evidence that Garza’s defense improved considerably this season.  Let’s first look at his blocked shots and fouls committed.  The table below shows the percentage of the opposing team’s two point shot attempts that Garza blocked as well as the number of fouls that Garza committed per forty minutes.

Garza increased shot blocking while reducing his fouling rate
Fr 4.6 4.5
So 2.6 3.9
Jr 6.0 3.1

As you can see, Garza blocked some shots as a freshman but committed a lot of fouls in the process.  As a sophomore, he cut down on the fouls but the blocked shots went away in the process.  As a junior, however, the blocked shot rate more than doubled, exceeding his freshman year, while continuing to reduce his fouling rate.  This is dramatic improvement.  A 6% shot blocking rate is not elite (10% is about where I’d draw the line for that) but it is still very solid (101st, nationally, out of 3000+ players). 

You may recall a Franalysis article from last year calling for more shot blocking from Garza.  Well, he made that improvement happen, and Iowa's team-wide shot blocking rate improved from 9% to 10.6% in spite of the fact that Nicholas Baer, the team's best shot blocker from a year ago, graduated.  Iowa's two point defense improved from 53.5% to 50.3% and, although there were a lot of new pieces on this year’s team, the correlation between shot blocking and two point defense is strong enough that it's fair to attribute most of this improvement to Iowa's improved shot blocking and to Garza, specifically.

There is other statistical evidence for Garza's improvement.  For example, the cohort of Big Ten centers that Garza went up against averaged 11.7 PPG on the season.  They only averaged 10 PPG against Iowa.  There are several defensive metrics out there that attempt to use a player’s box score stats, and his team’s overall defensive efficiency, to estimate the quality of his defense.  An analyst named Dean Oliver (no, not that Dean Oliver) devised a pretty intense algorithm for individual defensive rating.  The formula can be found here.  Bart Torvik has an (in my opinion) improved version of this that factors in quality of opponent that he calls D-PRPG.  Last year, Garza’s D-PRPG was a mediocre 2.2 (1114th among D1 players).  This year, he upped that to 3.8 which ranks 145th among D1 players (approximately 95th percentile).  These stats tend to be dominated by big men, since they are largely based on blocks and defensive rebounds, but still, his improvement was colossal.

Lastly, I tracked every possession that Iowa team played this season, with the exception of the games at Maryland, home against Illinois, and the Ohio State game.  At first glance, these numbers are not flattering to Garza (Iowa allowed 1.03 points per possession when Garza was in the game and 0.98 points per possession when he was out).  However, there is a hidden variable in those statistics:  Cordell Pemsl.  For some reason, and this will be the topic of another article down the road, Iowa was waaaaay better defensively when Pemsl was in the game, allowing 0.93 points per possession when he was in the game vs. 1.05 points per possession when he was out of the game.  Pemsl tended to play most of his minutes with Garza on the bench, which skews the data. 

To correct for this, we can restrict the analysis to possessions where Pemsl was in the game.  Within this set of possessions, Iowa's defense improved by about 0.04 PPP when Garza was also in the game. Alternatively, we can specifically analyze possessions where Pemsl was out of the game.  Here the defense improved by about 0.02 PPP when Garza was in the game.  These numbers are given in the table below.  One tricky thing about this type of analysis is that it isn’t a direct measure of Garza’s defensive quality, rather it is a comparison between Garza and his backup(s): generally Kriener, who is a solid defender in his own right.  In fact, during the 2018-19 season, Iowa's defense got about 0.07 PPP better whenever Kriener was on the floor (typically at Garza’s expense) and about 0.05 PPP worse whenever Garza was on the floor.  During the 2019-20 season, though, the defense was better with Garza on the floor, when the confounding effects of Pemsl are corrected for.

Iowa's defensive efficiency, with and without Garza/Pemsl
Garza In Pemsl In 0.91
Garza Out Pemsl In 0.95
Garza In Pemsl Out 1.05
Garza Out Pemsl Out 1.07

The bottom line here is that, as much well-deserved praise as Garza's offense receives, he also made significant improvements on the defensive end that were instrumental in Iowa's success this season.  These improves are attributable to his extraordinary work ethic and toughness.  Let's all hope that he tries to reach another level at that end of the floor and that he decides to do so in an Iowa uniform.

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