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Nylon Calculus: Freedom of movement and stoppage of play

By Scott LaForest

WASHINGTON, DC - FEBRUARY 8: Referees: Bill Kennedy, Leroy Richardson and Kevin Scott huddle up during the Boston Celtics game against the Washington Wizards on February 8, 2018 at Capital One Arena in Washington, DC. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this Photograph, user is consenting to the terms and conditions of the Getty Images License Agreement. Mandatory Copyright Notice: Copyright 2018 NBAE (Photo by Ned Dishman/NBAE via Getty Images)
WASHINGTON, DC - FEBRUARY 8: Referees: Bill Kennedy, Leroy Richardson and Kevin Scott huddle up during the Boston Celtics game against the Washington Wizards on February 8, 2018 at Capital One Arena in Washington, DC. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this Photograph, user is consenting to the terms and conditions of the Getty Images License Agreement. Mandatory Copyright Notice: Copyright 2018 NBAE (Photo by Ned Dishman/NBAE via Getty Images) /
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The NBA Board of Governors made some big changes for the 2018-19 season. The biggest change was the reset of the shot clock to 14 seconds after an offensive rebound and the possible effects of this rule change were analyzed extensively prior to the season, including here on Nylon Calculus. The other change was an emphasis on the freedom of movement.

Not only does the NBA make rules changes every year but they typically have official “Points of Education” for the referees to emphasize throughout the season. Watch this video to see NBA Vice President and Head of Referee Development & Training, Monty McCutchen, discuss the freedom of movement emphasis. McCutchen explains the specific actions that the referees are looking for freedom of movement violations, both in the post and on the perimeter. On the perimeter, the NBA defines freedom of movement violations as “impedes, wraps, and contact on screens”.  This includes grabbing of jerseys or body parts of the offensive players as well as aggressive contact on cuts and screens.

In the post, freedom of movement includes “grabs, dislodges, and contact on post moves to the basket.” It is more typical for both offense and defense to be whistled for a foul in the post as both offensive and defensive players can impede the freedom of movement of the opposition.

I wanted to see how the freedom of movement emphasis has changed the game so far this year.  Using a combination of data from stats.nba.com and pbpstats.com, I gathered information on fouls drawn and free throw attempts. First of all, personal fouls drawn (PFD), free throw attempts (FTA), and percentage of points from free throws (FTM/PTS) are all up over last year. We must be careful to compare counting stats such as PFD and FTA as the pace throughout the league is also way higher than it has been in the past. With pace and possessions trending higher, teams should be drawing more fouls and taking more free throws.

So I looked at personal fouls per 100 possessions and free throw attempts per 100 possessions. As a side note, I thought about using FTA Rate but chose FTA per 100 possessions as it has a similar range to PFD. I also gathered data on the non-shooting fouls compared to FTA from pbpstats.com.The graph below plots the league average percentage of points from free throws, the per 100 possessions stats for PFD and FTA, and the ratio of non-shooting fouls to total FTA for the last 15 seasons.

nba ft and fouls drawn plot
nba ft and fouls drawn plot /

As we see from the graph, these three stats have been trending down for most of the last decade. Through the first quarter of the 2018-19 season, we have seen a statistically significant increase in PFD and FTA per possession and a slight uptick in points from free throws.  Looking at the ratio of FTA to PFD we can see that 2018-19 has the smallest ratio of FTA to PFD of 1.07 FTA per PFD. The second smallest ratio happened to be in 2017-18 at 1.09. The smaller ratios might have more to do with the emphasis on jump shooting throughout the NBA.  Also, the ratio of FTA coming from non-shooting fouls took a drastic leap up this year and is the highest in the last 15 years.

Also from the above graph, we have had the largest increase in fouls and foul shots since the 2004-05 season.  Back in 2004-05, the NBA implemented hand check rule which limited the defense from placing their hands on the offensive ball handler. The 2004-05 season had a greater increase in FTA but this year so far has the larger increase in PFD. Because of rule changes both 2004-05 and 2018-19 are leading to increased foul calls and free throws. Using the hand check rule as a guideline we can expect the league to adjust, it just might take a season or two.

The second part of this analysis will look at which teams are benefiting the most from the new emphasis. I looked at teams with the biggest change in possession-based PFD and FTA. The chart below is segmented into columns based on the amount of change from 2017-18 to 2018-19.

NBA team diffs FTA PFD 2018
As we can see some of the biggest increases in FTA are the Dallas Mavericks. The Mavs increased their FTA per 100 possessions from 19.4 to 25.6 for an increase of an extra 6.2 FTA per 100 possessions.  With a team free throw percentage of 75 percent, that means the Mavs are getting an extra 4.65 points per 100 possessions this year over last. The increase in FTA could be attributed to bringing in more quality creators such as Luka Doncic and revamping their style of play to feature his dribble-drive attacks. /

On the other hand, the Detroit Pistons have the largest increase in fouls drawn this year, with two quality bigs in Andre Drummond and Blake Griffin, both of whom draw a lot of fouls. New Pistons coach Dwane Casey is also known for having an offensive philosophy that emphasizes movement and drive-and-kick opportunities. With the new freedom of movement emphasis, Casey and the Pistons have an offense that has taken advantage.

Next. Checking in on this year's NBA rookie extensions through 20 games. dark

With the emphasis on freedom of movement, the NBA is attempting to make the game more open and free-flowing. So far the emphasis has led to more stoppage of play due to foul calls and free throws. From an entertainment point of view, this might hurt a little right now. I’m willing to bet that most NBA fans would prefer watching players launch a deep 3 or a cut to the rim for a nasty dunk instead of free throws and sideline inbound plays. As teams adjust we should see the number of whistles decrease and players moving more freely, especially on the perimeter. This is good news for fans of the modern NBA and especially for players that rely on movement to score.

Guys like Steph Curry, J.J. Reddick, and other active catch and shoot specialists should benefit. Post play also should be a little cleaner on both sides as arm bars, shoves, grabs, and the infamous knee-to-the-backside dislodgement should be eliminated. I do think that the new freedom of movement is positive as it removes some of the defensive tomfoolery and overly aggressive physicality from the game. It just might take some patience as the players and teams adjust to accommodate the new rules.

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