The Upside Down Celtics

 

Over at the Nylon Calculus, I noted that the Celtics have sometimes been accused of having an upside down line up, in the sense that the back court players can't shoot and the front court players can't play defense. In that post I was looking at a study using a stabilized version of plus/minus data called RAPM that indicated that, while the traditional stereotype was in some ways true there may be an important caveat.

To put it succinctly, guards, on average, contribute more on offense and less on defense,while for centers and power forwards the opposite was true. But the interesting bit is that the spread between the best and worst center on defense and the spread between the best and worst point guard was largely the same.  

If guards really weren't important to defense we would expect the spread between the best and worst point guard to be much much smaller than for centers since it wouldn't matter, for example, if Aaron Brooks, ones of the worst PG defenders or Chris Paul, one of the best, was on the court.  The RAPM data and a more complicated version that combines box score data called Real Plus Minus (RPM), via ESPN, indicate otherwise.

So, in theory, this data indicates that it wouldn't necessarily be bad that the Celtics were  'upside down' on defense.  One would always prefer to have five good defenders on the court and five good offensive players, of course, but it is not inherently less valuable to have an elite defensive guard replace an average guard than an elite center replace an average center.

Focusing on the defense, I put this table together with the defensive RPM scores of the Celtics' current roster, excluding the rookies.  It has each player's raw D-RPM, then adjusted for position and their percentile rank for their position.

 

So, how upside down is this roster?  Outside of Olynyk and Bradley, and perhaps Marcus Smart who projects very well as defender, the Celtics roster is actually not all that upside down.

Based solely on raw D-RPM one would be lead to believe that Joel Anthony, Jared Sullinger, and Tyler Zeller were the C's best defenders, after Gerald Wallace.  However, Sullinger, Anthony, and Zeller are all just average for the their position, indicating they're adequately filling their defensive role but not little more.  

Based on the Position Adjusted column, however, the clear difference makers on defense for the Celtics were Gerald Wallace and Avery Bradley, both of whom are above the 90th percentile and rate 2.4 points per 100 possessions over position average on defense. (Side note, Bradley is listed as a point guard by ESPN, despite manifestly NOT being a point, though for defensive purposes guards are ranked together here as there was no significant difference on defense).

On the other side, while Rajon Rondo and Kelly Olynyk both rate near the bottom on raw scores. Rondo, despite his reputation, scores a little below average for his position,but Olynyk is much much worse when position is taken into account.  A little of that can be attributed to listing Olynyk as a center, where his more natural position is power forward, but he would still be last on the team by a wide margin.  

Olynyk scores poorly on Rim Protection using SportVu data, allowing opponents to shoot well above average on contested shots near the basket for a big man at 54.6% (average being 50%). But, the team as whole faired no worse protecting the rim with Olynyk on the court, according to NBAWOWY data.  However, Olynyk fouled too often when he did try to protect the rim, a stat that shows up in even the raw on/off data for the team, with the free throw rate jumping from 28% to 32% for opponents when Olynyk was on the court.

Olynyk as a big man that can shoot from outside and pass, has the potential to be the Celtics most complete offensive player, but in order to impact the game positively he will need to learn passable defense.

This is the part of the post where I add the caveats and disclaimers about RPM as a stand alone metric.  It is not perfect, with a single year there are multi-co-linearity issues, which adds to noise.  There are always factors on defense that emerge from the combination of players that can't be completely isolated to individuals.  But RPM does have a decent track record, with its predecessor xRAPM, in terms of prediction.

Like any metric or stat we expect some reversion to the mean next year, adding to that an aging factor, the safest predictions are that Olynyk's defense will improve and that Bradley's and Wallace's, especially, will get worse.  Making the defense that much less upside down, though not that much better.

Comments

[Mojo_Filter]

Andrew, Really liked this one + the Nylon Calculus article on "Does Guard Defense matter?". What's the tipping point Offense to defense when one factor over rides the other?

I have a question regarding a totally different subject (wasn't sure how to contact you directly)

Have you or any of your cohorts done any work towards attempting to figure out how to "Rate"
NBA coaches?

I've been poking around Google for about an hour and have yet to find a ranking/rating system that offers anything more than some touchy feely attempts to do this.

I'm not even sure how to approach it or even if there's data that can be gotten at to do so,

I cam across an interview with Bill Musselman commenting on Brad Stevens right after his hire and he lists what he believes are the difference between coacing in the collegiate ranks vs the pros.

http://www.azcentral.com/sports/asu/articles/20130705asus-eric-musselman-knows-what-brad-stevens-faces-with-the-celtics.html

It breaks down to Personnel, Teaching, The Shot Clock, Late-Game situations (see below) and Practice (PRACTICE??!!)

Not sure if this is a good baseline for attempting to do a rating/ranking or how Coash "A"'s
substitution pattern would work with Coach B's team etc etc.

There's also an attempt to analyze ​Which NBA Coaches Are Best At Designing Plays During Timeouts. http://regressing.deadspin.com/which-nba-coaches-are-best-at-designing-plays-during-t-1482773198

Which looks like it could be part of an analysis based on somthing tangible.

Ideas? Comments?

[Andrew]

Thanks for the comment. I took a pretty incomplete look at coaching last year, I think Jeff Hornacek came out the best. Some studies like Dave Berri's think the most important aspect of coaching is just putting the right players into the game. I also think Jeremias Engelmann has done some stuff on coaching, he used it in his original version of RPM.

[Andrew]

Here is the coaching post I did last year.
http://counting-the-baskets.typepad.com/my-blog/2013/12/coach-effect.html

[twitter.com/KWAPT]

Wish I had the patience to go through all these stats/ratings. Thanks for doing it for me though-enjoy your blog.