The benefit and the cost of the assist

Brett Davis-USA TODAY Sports

Assists lead to better shooting ... and turnovers. Does the data suggest that focusing on boosting a team's assist percentage pays off in the end?

As I watched my Sacramento Kings lose in embarrassing fashion once again on Sunday, all while tallying up 13 assists in an entire NBA game, I started thinking about passing, its benefits and its consequences. The Kings don't pass, and they don't shoot well. Everyone seems to take more shots off the dribble than is necessary. But then you have teams that do make an effort to pass a lot ... and they tally up lots of turnovers. Many point guards, in particular, have that problem. And it's an important question: is the benefit of getting a better shot worth the potential for a turnover?

Think about the theory of it. In theory, anyone with the ball can attempt a shot. A point guard can drive on his man, take a pull-up or go all the way to the rim. A wing can face up and take a shot or drive the lane. A big man can whip out a post move or attempt a turnaround. These are all shots. But they're not all good shots. And the point of an offense is to get better shots. Passing helps. In theory, it allows you to create openings, find openings and exploit openings. It makes perfect sense that offenses with more passing would get better shots.

But in theory, it also makes sense that offenses with more passing would have more opportunity for turnovers. And a turnover is the only thing worse than bad shot. In particular, passing turnovers are the second worst type of turnover, behind only the offensive foul. (The offensive foul is not just a turnover, but obviously a personal foul, which has an impact on the offender's availability and the opponents' free throw rate.) Other turnovers like the shot clock violation and traveling are dead ball turnovers: the opponent will gain no transition advantage from the turnover. Passing turnovers and live ball steals result in transition opportunities. (Whether those are capitalized upon depend on the thieves' ability to finish in transition and the team's own transition defense. But over time, transition possessions come out ahead of halfcourt ones.)

So is the benefit of passing to shooting percentage worth the consequence of a higher turnover rate? Where's the breaking point?

What's interesting to me is that the data doesn't back up the theory that teams that pass more effectively get more of what we consider valuable shots.

There are two ranges in the halfcourt that produce points most efficiently: within three feet of the rim and behind the three-point arc. Players are shooting 64 percent at the rim this season and have an effective field goal percentage of 53 percent on threes. (Effective field goal percentage adjusts for the added points value of a made three.) From everywhere in between, players shoot 38 percent on average. So it's much better, as else equal, to get shots at the rim or from behind the arc than on short to long two-point jumpers.

You would think this is where passing helps: in getting those more valuable shots. Alley oops. Corner threes. Nope. The correlation between a team's assist percentage (the share of made field goals there was an assist on) and the frequency they take the more valuable shots is negative. On the whole, teams that do a lot of passing and assisting end up taking more two-point jumpers (the least efficient shots in basketball) than teams who do not.

That's not a great argument for assists, is it?

But the value of the assist comes out in another area: conversion rate of those valuable shots. Teams that pass and assist a lot convert shots at the rim and three-pointers at higher rates than lower-assist teams. The correlation is strongest on threes: assist percentage is strongly correlated with three-point percentage, and moderately correlated with shooting percentage at the rim. The correlations with shooting at other ranges are positive, but much smaller. So while being an assist-heavy team doesn't necessarily get you more good shots, it seems to correlate well with turning those good shots you do get into points.

So here's the rub: we know taking more of the valuable shots (at the rim and threes) really helps an offense. (The correlation between frequency of those shots and overall team shooting is strong.) But we see that having a strong passing game doesn't create more of those shots. But it does help you convert those shots. So how do you combine the benefits of getting more out of those shots through assists if the assists don't help you get more? How can you get more good shots without setting them up via pass?

(My guess: offensive rebounding and a couple of strong isolation players to soak up the typically inefficient shots.)

This whole discussion only scratches the surface, and no matter what the correlations say each team will have its unique strengths and weaknesses. But, for me, it helps ascertain why the Kings' offense is so ugly despite getting a high number of shots at the rim. The lack of passing isn't helping those shots or the team's three-pointers go in. DeMarcus Cousins creating for himself in the paint is a lot different from Chris Paul lobbing a pass to DeAndre Jordan. It's all in the execution.

In the end, on the question of the value of the assist, it turns out that the correlation between assist percentage and offensive efficiency (points per possession) is basically nonexistent. How well you shoot determines roughly half of how good your offense performs. Turnover rate is about 20 percent. So it makes sense that while assists have a smaller impact on shooting than on turnover rate, the outsized impact of shooting on an offense overall makes them even out. Again, it's all in the execution. If there's light to be shed here, it's that passers who can rack up assists without committing turnovers are perhaps most valuable. Free Brevin Knight.

***

The Hook is an NBA column by Tom Ziller. See the archives.

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