Is the Trail Blazers' Ball Movement Stagnating?

Passing is en vogue right now in the NBA. Teams that move the ball well, like the Spurs and Warriors, win games, says the conventional wisdom.

The Portland Trail Blazers, while not as impressive as the Spurs and Warriors, are also great passers. Whether it's Damian Lillard's utilitarian exploitation of a collapsing defense, CJ McCollum whipping a pass around the head of a defender, or Meyers Leonard hitting a backdoor cutter, the Blazers know how to find the open man:

Passing and player movement are the essential elements of coach Terry Stotts' flow offense ("Stottsfense" for short), so it is no surprise that we've grown accustomed to seeing passing highlights. Impressively, Stottsfense has also kept the Blazers' offense in the top 10 this season despite the massive roster upheaval last summer. It's safe to say the system is working.

Given Portland's offensive prowess, it's thus surprising that the Blazers are defying conventional wisdom and currently sit at No. 25 in the league in total passes per game and No. 24 in the league in passes per possession. That's only three spots ahead of the notably stagnant Lakers.

The effectiveness of the Blazers' passing does rank somewhat higher, but is still no better than league average in nearly all categories. Per stats.nba.com, the Blazers are No. 20 in assist percentage, No. 14 in potential assists (all plays that would have ended in an assist if an attempted shot had been made), and No. 16 in points created by assists.

Taken together, these stats suggest that the Blazers are producing points efficiently with a below average amount of ball movement. The low assist rate also suggests that this is not a case of "doing more with less" - when they do pass the ball they're not any better at generating open shots than an average team. According to conventional NBA wisdom, the Blazers are an offensive anomaly.

How are the Blazers good at offense but bad at passing?

The most obvious answer is that the Blazers get 44 percent of their points from their ball dominant combo guards McCollum and Lillard. The Blazers' starting backcourt scores points largely on their own; they are assisted on less than 33 percent of all their made field goals. Ed Davis is the next closest Blazer at 56.5 percent.

The Blazers run a huge number of pick-and-rolls with McCollum and Lillard as the ballhandler. On the season, Portland is third in pick-and-rolls (19.5 percent of all possessions), and McCollum and Lillard are fourth and eighth, respectively, in total pick-and-rolls. These plays rarely lead to more than two passes, and very often have zero passes. Of those possessions, the roll man receives the ball and initiates the possession ending event less than a third of the time.

McCollum and Lillard are, effectively, working out of isolation for a huge number of possessions per game, driving down all of the Blazers' passing numbers. The two guards are effective in that role; both are in the top 20 percent for points per possession on pick-and-rolls.

The Blazers are also not great at converting assist opportunities that are generated. Only 49 percent of the team's potential assists turn into actual assists, No. 18 in the NBA. That suggests that either poor shooters are receiving passes, players are not being found in their comfort zone, or the offense is not getting open looks. More review of tape and tracking data would be required to definitively answer this question, but it is worth noting that this ineffectiveness may be de-incentivizing ball movement.

Does it matter?

I opened this column by mentioning the conventional wisdom that ball movement is a sign of good offense. Passing certainly looks aesthetically pleasing, but the Blazers provide at least one example of a team with an above average offense and below average rate of ball movement. Are the Blazers an exception, or do other teams follow the same pattern?

To answer the question, consider this graph of passes per possession charted against offensive rating (dashed lines are league averages):

Note: The NBA does not list passes per possession on its stats website. I calculated this measure by dividing a team's passes per game by its pace (defined as possessions per game).

Some teams did perform as expected. For example the Lakers are in the far bottom left quadrant meaning they don't move the ball well and they rarely score; a sentence that has been used to describe the team all season. But the results, when considered on the whole, belie any clear pattern. The Warriors, Spurs, and Thunder have the top three offensive ratings in the league but differ greatly on their number of passes per possession. Meanwhile, the 76ers pass more than the league average, and even more than the Warriors but have the worst offense by a wide margin. These data strongly suggest that passing does NOT correlate with a high offensive rating (for stats nerds: p = 0.833, r = 0.040[!]).

Teams do tend to cluster more closely on offensive rating as passes per possession increase toward the average, excluding outliers. This might suggest that teams that move the ball with an even close to average frequency are always able to get some clean shots, but have difficulty becoming elite. Teams that rely more heavily on isolation, on the other hand, are more likely to sink or swim depending on the offensive skills of their top players.

Circling back to the Blazers, these results are good news. They suggest that the quasi-isolation heavy offense the team runs is not necessarily a problem. The Blazers could develop an elite offense, like the Thunder or Clippers, without moving away from the McLillard show. They are also at greater risk for an offensive drop should either of their stars become ineffective.

Note: The Blazers' position on this chart relative to the Mavericks and Rockets is interesting. Dallas, a team often linked stylistically to Portland, is extremely far away on passes per possession. Houston, a team considered different from Portland based on its heavy use of ISO sets as opposed to the Stottsfense flow offense, is very close to the Blazers in both effectiveness and ball movement. Perhaps the Lillard/James Harden comparison featured on Blazer's Edge last week has even more validity than realized.

Conclusion

The Blazers often appear to be a good passing team, regularly generating highlight ball movement clips by working within Stotts' offense. The transcendent skills of Lillard and McCollum, however, have placed ball movement on the periphery, in favor of a quasi-isolation offense. Contrary to popular believe, passing does not correlate with strong offense in the modern NBA, so the Blazers are not putting themselves at a disadvantage by relying heavily on two players to create shots at the expense of ball movement. Indeed, many teams have thrived with many different strategies. The most extreme examples being the nearly isolation-exclusive Thunder, and the pass happy Spurs, both of which are among the league leaders in offensive effectiveness.

h/t to Nylon Calculus for pointing out how rarely the Thunder pass while maintaining an elite offense.

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