Dec 17, 2014; Boston, MA, USA; Boston Celtics guard Rajon Rondo (9) on the court warming up before the start of the game against the Orlando Magic at TD Garden. Mandatory Credit: David Butler II-USA TODAY Sports
How will the Rajon Rondo trade affect Dallas’ offense? The short answer is we have very little real idea. On one hand his own scoring efficiency is laughably bad so far this season, with a true shooting percentage of 0.422. On the other side of the ledger, Rondo’s offensive value has never been in his scoring. With Boston’s contending teams, his usage rate was always below average. His role was far more to set up the Celtics more efficient scorers like the big three or to allow players completely dependant on being set up for good shots (such as Brandon Bass or even James Posey) to get those looks.
Now, in Dallas without the burden of being “the man” any longer, perhaps that is a role to which he’ll be returned. Yet it’s a role that, from an analytics standpoint, we know very little about.
Valuing playmaking is controversial, in part because there isn’t really an agreed upon description of the word. Certainly, the “assist” is an imperfect and at times even corrupt unit of measurement. That said, we do have some more insight on both the value of playmaking at the team level and a better way to describe individual playmaking through a few years of SportVU data.
On the team level, assisted shots are significantly more valuable than unassisted shots. Last season, the difference was about .3 points per shot, league-wide. How much of the credit for this goes to the passer compared to the shooter compared to the overall offensive system? Very much a good question.
Similarly, with the SportVU data we can look at individual players’ share of this playmaking. Part of my True Usage statistic is tracking what I’ve termed “Assist Usage,” or the proportion of plays where a guy makes a pass leading to a scoring attempt.
So what does this mean for Rondo to the Mavs? It will be a fascinating test — Dallas was roughly league average both in terms of proportion of assisted shot attempts and in their efficiency on those shots at the time of the trade. However, their overall efficiency was so high in large part because of their ability to make unassisted shots. They have nearly a 47% Effective Field Goal Percentage on those attempts[1. compared to NBA average of around 41%]. So despite their whirring, fizzing machine of an offense, playmaking has been less important to their success than might be expected. Still, like every other team in the league, they shoot much better on assisted shots.
Which brings us to Rondo. So far this season, he’s the only player with an Assist Usage north of 30%[2. Ricky Rubio, when healthy was passing at a similar rate, but his injury has kept him out of the lineup for too many games to qualify]
Aside from J.J. Barea’s spot duty, no Mavericks have a particularly high rate. The departed Jameer Nelson was next at 17.3%, while Monta Ellis, often said to be Dallas’ point guard in all but name, is only setting up 14.4% of teammates shots[3. League average for PG’s is right around 19%].
So, will Rondo increase Dallas’s overall “passiness” and will that be enough to offset the downgrade in floor spacing and shooting from Nelson to Rondo? This will be a fascinating experiment on that front. While there is some understanding of how players’ roles may change and shift in terms of traditional (shooting) usage when new talent is added or subtracted, very little at all is known about how dropping a player of Rondo’s playmaking skill into the mix will alter that aspect of the offense. Part of the difficulty in predicting the effect is while their is a hard and inviolable limit to a team’s total shooting usage (there is only one ball, and only one player can shoot each trip), the same does not hold for creating assist chances — there is a wide spread between the most (Atlanta at 61.3% of shots potentially assisted) and least (Toronto at 45.7%) prolific teams in terms of creating for others. How far, if at all, Rondo moves the Mavericks towards the upper end of that range will be something to keep an eye on for the rest of the season.