Counting the Baskets

RSCI Draft Model

Quick post on an in process update of my draft model. Essentially I am working in the consensus high school ratings provided by the Recruiting Services Consensus Index (RSCI) for college basketball.

There are a couple of challenges to this, the first being that not every top pro prospect gets a RSCI rating, especially when looking at foreign prospects. Second, in the analysis I found that there is a quick degradation of the information conveyed by the ratings, which can reach into the hundreds. Essentially for NBA prospects I was only able to pick up a signal in the top twenty or so rankings, and even then a log scale transformation seemed to pick up information best in the training data. Keep in mind, for example, that the current favorite for the regular season MVP, Steph Curry, was not even rated by the RSCI service, because he wasn't considered good enough in high school to even rate.

Age entering the draft and RSCI rating are positively correlated. Essentially players who are highly rated coming out of high school are more likely to enter the draft earlier, because of the regard scouts and teams hold them in, and, therefore, the more money they can make by leaving. A less heralded player may both take more time to earn a starting position on the team and even with a similar freshman year performance would be more likely to stay in school as a first round selection would be far from guaranteed until a longer record of high performance is demonstrated.

Therefore, the biggest single difference, other than the new variable, between the RSCI-PAWS (beta) and the PAWS model is the age adjustment. The age coefficient falls be approximately 13% by including the RSCI ratings, which ends up aiding some non-blue chip rated prospects entering the draft a bit older.

In terms of draft order the most significant difference is Jahlil Okafor moving from third to first, and D'Angelo Russell moving from first to second. Willie Stein also moves up due, in part, to the lessened emphasis on age.

Fitting Marcus Smart in the Celtics Back Court

Mandatory Credit: David Butler II-USA TODAY Sports

Originally post on Nylon Calculus on 1/02/2015

As soon as the Celtics traded Rajon Rondo to the Dallas Mavericks some pundits announced the move as the start of the Marcus Smart era. However, in the first six games since the trade it has been less clear that any particular era has dawned, certainly at the point guard position.

Celtics Coach Brad Stevens has started three different players at point guard in the six games: Evan Turner, Jameer Nelson and Smart. Stevens returned to Turner on a New Year's Eve matinee after Smart's rough start in Washington, which was perhaps his worst game as a pro so far. Smart was pulled early in the first quarter after four quick turnovers. With that short hook, Smart has averaged just 24.2 minutes in since the trade.

As soon as the Celtics took Smart with the sixth pick in the draft there were superficial comparisons made between Rondo and Smart—players who played point guard in college with a reputation for defense and a somewhat shaky jump shot. However, at the point guard position there is a tremendous difference in the two player's passing and distribution level. Rondo, both stylistically and statistically, is one of the best passers in the NBA, while Smart is, at this point, essentially a combo guard. Smart's 4.2 assists per 36 minutes of play rank him at 76th out of guards with at least 250 minutes played this year, per Basketball Reference, in the same range as combo guard types like Victor Oladipo and O.J. Mayo. His assist rate of 5.0 per 36 since the trade would rank him at 59th. His Assist% numbers tell largely the same story.

There are a couple of ways to illustrate this, using simple assists per 36 minutes, assist percentage, points created by assist per 48, and percent of two point shots assisted, in nearly all measures Rondo is elite, while Smart has performed (and been used) more as a combo guard. Below are those measures for Rondo, Smart and rest of the Celtics rotation players.

 

Smart's assist numbers are clearly below the more traditional point guards like Rondo, Phil Pressey, and Nelson. His points created by assist per 36 minutes (scaled to match the Basketball Reference numbers), are about one third of Rondo and Nelson and less than Turner, who, for now, has won the starting point guard position. Jared Sullinger and Kelly Olynyk show up as plus passers for their positions, but still below typical guard level.

Another statistic I like to look at in terms of ball handling aptitude and responsibilities, which is in the far right column above, is the percent of a player's made two point shots that were assisted. Last year I used that stat both to group guards into 'shot creation' clusters and to project that Jordan Crawford would grab the starting point guard spot until Rondo returned from his knee injury. In terms of percent of two pointers assisted, Smart's numbers are in line with typical 'creator' point guards. But, in the second most telling measure I used, he is only attempting shots at the rim at a rate of about 2.5 attempts per 48 would have been more in line with a being a 'Spot Up' point guard, which SportVU data indicates is mostly because of his lack of drive attempts at the basket.

Drives and Line Up Balance

In half court sets the ability of a team to break down a defense off the dribble in drives to the basket is a valuable weapon, For example, Steven Shea, at his blog Basketball Analytics Book, found that team Drive efficiency explained 63% of total offensive efficiency last year and combined with corner three efficiency explains most of offensive efficiency. When Rondo was on the team he ran the drive game of the starting line up along with Jeff Green.

Thus far Smart has not shown much drive game at the NBA level, which is probably the biggest concern in his developmental progress. While there is no rule that drives need to be performed by the point guard, if Smart is injected into the Celtics starting back court with Avery Bradley there may not be much other choice. Below is a table with the Celtics' drive statistics from NBA.com to highlight the fit issues Stevens is dealing with fitting together a back court.

Rondo, Pressey, and Nelson have all averaged nearly ten drives per 48 minutes with the Celtics, with Turner driving just below seven times. Bradley averages 2.6, fewer drives per 48 minutes than either Olynyk or Sullinger, while Smart's 3.5 is just about the same as Sullinger. With Smart and Bradley in the line up it's not clear the Celtics' starting line up would have enough dribble penetration on the court outside of Jeff Green, who drives well with the most efficient production per drive on the team, but with one of the highest percentage of points generated for himself rather than teammates. Added to this is that Smart has the lowest points generated per drive on the team.

Looking at these numbers it is tough to see how a Bradley and Smart starting back court would be successful offensively at this point in Smart's development. Putting Nelson in the starting line up might create too many defensive issues, especially along with Bradley since the Celtics like to have him sometimes cover the opposing point guard. That leaves the starting combo Stevens used on New Year's Eve, or starting Smart alongside a more creative back court mate.

Draft Model Update 1-3

I re-ran my Draft Model built last year against the Draft Express Top 100 prospects. I haven't added any work on the basic model, which projects player production in the final two years of a player's rookie contract.

This one has performed pretty well to date, both in and out of sample, but I have some ideas to possibly improve it looking at a better measure of overall/potential production that I may try to look at more closely when the spring comes.

In any case there is slowly but surely a better sample of the current prospects building. Interestingly there is still a pretty wide gap between the model's projections and the consensus top picks, I expect some of that to close based on last year. Players who are performing above their skill level will see their numbers slide and the consensus will adjust to some degree on disappointing players when the draft comes more into focus.

In any case, based on the numbers from DraftExpress through January 3, 2015 here are the top thirty prospects as rated by my model, with thanks to Darryl Blackport. (For reference Anthony Davis was projected as a 9.1, Nerlen Noel as a 7.8, and Jabari Parker as a 6.3, a typical NBA starter would be about 5.5)

(Update: Original post had the wrong birthdate for Robert Upshaw, calculating him as 18 years old, he will be 21 at the 2015 draft.)

The surprises on the list are Tyler Ulis and Fred Van Fleet on the upside, based on Ulis's youth and excellent production and VanFleet's good production this year along with even better numbers last year. The model weights production by minutes with the more recent year weighing more, so if Van Fleet doesn't return to the career numbers from last year his rating will fall.

On the downside Kelly Oubre, who has universally been judged to under perform and Justice Winslow also slides. Willie Cauley-Stein scored surprisingly lowly, so much so that I had to recheck the calculations. But, he is in part held down by age and not as impressive numbers last year, if this level of production continues, which the model is built to not expect, he will rise to the top ten in all likelihood.

I also have a Google doc here with the whole list here.