Nylon Calculus: Ball movement through the lens of assist distributions


Justin Rowan of Fear the Sword raised an interesting point about assists a week ago–– are we overvaluing high assist players and assigning a perhaps undeserved level of importance to double digit assist totals? Without getting into the branch of discussion of whether assists by themselves are a great indicator of playmaking or ball movement, it’s a fair question to ask just in the context of team success.

Although modern NBA offense is all about side-to-side ball movement and pace-and-space, stylistic preferences don’t necessarily correlate too heavily to offensive success. There are just as many teams who run good offenses through one or two players pounding the rock as there as teams who pass circles around their opponents. Continuing on that thread of ball movement, I decided to fire up Basketball-Reference and look at the distribution of assists amongst the top 10 offenses in the league this past season. For some consistency, I only considered the top 12 players in terms of minutes played for each team, and used the per-36 assist numbers. And as for the data visualization choice? I was leaning towards some sort of density plot, but as a wise Daryl Morey once said:

Below are the distributions of the total adjusted assists (having summed everyone’s per-36 assist numbers) for the top 10 teams in offensive rating last season.

There are immediately two types of teams that stand out–– teams with a single dominant assist aficionado and teams that share the ball movement load, as expected. The Rockets, led by James Harden, were the most extreme team, with Harden sopping up just over 30 percent of the total adjusted team assists. The Wizards (with John Wall) and the Clippers (led by Chris Paul) were close behind as well. The Warriors were of course on the other end of the spectrum, with five different players all averaging over 4.5 assists per 36 minutes.

With the Rockets, Wizards, and Clippers the paragons of single-player dominated teams and the Warriors, Spurs, Celtics, and Nuggets on the other end, it certainly seems to line up with our perceptions of how those various teams play. There’s no indication that one style is more successful than the other; it comes down to how well you can execute it with the available personnel. This is true today, and it was true ten years ago.

Well would you look at that? It’s certainly no coincidence that the Steve Nash-Mike D’Antoni Suns have one player carrying more of the assist load than any other team. Just like the Mike D’Antoni iteration of the Rockets from last season, the Suns were the only top 10 offense in 2006 where one player accounted for greater than 30 percent of the total adjusted assists. The other strikingly imbalanced team in 2006 was the Toronto Raptors, with two players — T.J. Ford and Jose Calderon — accounting for over 50 percent of the total adjusted assists, a mark that none of the top 10 offenses last season reached. Despite being led by highly effective point guards such as Chauncey Billups, Deron Williams, and Tony Parker, the Pistons, Jazz, and Spurs (respectively) were overall surprisingly balanced in terms of the distribution of assists.

But back to the present day and the overall context of team success. In terms of offensive styles, the Cavaliers and Warriors Finals trilogy has been incredible to watch in part because the two teams operate so differently. LeBron pounds the life out a defense on one hand, while Golden State subjects you to death by a thousand passes on the other. And their assists distributions reflect that.

As the Warriors assists distribution has gotten incrementally more balanced year by year, LeBron James accounted for a larger share of the team’s assists last season than he did in his first year back with the Cavaliers. From the 2014-15 season to last year, James averaged 7.4, 6.8, and 8.3 assists per 36 minutes. Over that same time span, Kyrie Irving averaged 5.1, 5.4, and 6.0 assists per 36 minutes. So to his credit, Kyrie is dishing more and more. The Cavaliers though, constructed in the top heavy manner that they are, just can’t squeeze assists out of their role players in the same way the Warriors have been able to.

But there is more to contextualizing team success beyond just the Cavaliers and Warriors. It’s widely accepted that the playoffs are a much different game from the regular season. Defenses become tougher, teams tighten up and game plan in a more focused manner, etc. With that noted, it’s intriguing to see if offenses adapt their ball movement accordingly. In order to check, for the top 10 offenses in the regular season last year, if they were a playoff team, I compared the regular season assists distributions to their work in the playoffs (with all standard sample size caveats still applicable).

Thanks to the Clippers’ perennial curse and Blake Griffin’s injury in the first round of the playoffs, Chris Paul accounted for a whopping 39 percent of the team’s total adjusted assists against the Utah Jazz. While Paul put up 9.6 dimes per 36 minutes, no one else on the team topped even 3.0 assists per 36. But aside from the Clippers, the other teams either mostly stayed true to their regular season philosophies or actually became more balanced in their distributions, most notably the Raptors and Wizards. While the Wizards’ playoff distribution is a little misleading thanks to Trey Burke and Tomas Satoransky notching 9.0 and 6.0 assists per 36 minutes respectively in very limited playing time, the Raptors had three different rotation players (Kyle Lowry, Cory Joseph, and Delon Wright) actually register over 5.0 assists per 36.

Next: Nylon Calculus -- Navigating the NBA’s changing landscape

Ultimately though, teams’ assist numbers didn’t suddenly start becoming more centered around one or two players in the postseason. If anything, the needle moved the other way. Unless you’re the Clippers that is. Given which, Chris Paul is probably really glad to be able to walk into a back court with James Harden and finally have someone else on the team who’s capable of competently running an offense.