Could a Focus on Free Throw Shooting Have Saved Sam Vincent?

Posted on September 22, 2008 by


Henry Abbott – of TrueHoop – posted a comment on Monday discussing the worst free throw shooting team in the NBA in 2007-08.  The team in question is the Charlotte Bobcats.  Charlotte – as Abbott emphasized – missed 605 free throws last season.  This stat prompted Abbott to state:

Can you imagine how their season would have been different if you could have given the Bobcats an extra 100 points to spread around their season? They would have won games that they lost. Several of them. They would have felt confident and proud. They would have likely been fouled less, and gotten cleaner looks.

I bet this is the kind of thing Sam Vincent thinks about sometimes.

Free Throw Shooting and Wins

This comment led me to wonder… exactly how many games did the Bobcats poor shooting from the charity stripe cost the team in 2007-08?

To answer this question we must first look at how the Bobcats shooting compared to the league average.  An average team hit 75.5% of their free throws last season.   Charlotte only hit 71.4% of their shots.  Since Charlotte took 2,115 free throws, a 4.1% increase in shooting efficiency would have resulted in 87.5 additional made free throws.  Such an improvement would have caused Charlotte’s points scored per game to increase from 97.06 to 98.13.  And this would have increased this team’s offensive efficiency (points per 100 possessions) from 101.8 to 102.9. 

Because Charlotte’s defensive efficiency was 106.4, this improvement in free throw percentage would still have left this team below the 0.500 mark.  In fact, this leap would only result in about three additional victories.  And since three more wins wouldn’t have vaulted the Bobcats into the playoffs, fixing this problem probably wouldn’t have been enough for Vincent to keep his job.

Can You Fix Free Throw Shooting?

Then again, if the Bobcats would have won three more games the franchise would have set a record for wins in a regular season. So maybe this would have kept Vincent employed (I don’t think this is true, but for this post to continue we will pretend). 

This, though, leads to another issue.  Is there anything Vincent could have done to change Charlotte’s performance at the line?

To answer this question, I am not going to address specific coaching techniques.  No, I am simply going to assume that coaches would want poor shooters from the line to improve.  Given this desire, if this aspect of coaching was effective, we should see performance from the line change over time.   

To see if this happens, I looked at how free throw shooting typically changes across a player’s career.  Looking at players who attempted at least 100 free throws in a season from 1991-92 to 2007-08, here is how free throw percentage varies with experience:

Year 1: 71.8%

Year 2: 72.9%

Year 3: 73.8%

Year 4: 74.3%

Year 5: 75.0%

Year 6: 74.5%

Year 7: 75.6%

Year 8: 76.3%

Year 9: 76.4%

Year 10: 76.4%

At first glance it looks like coaching might have an effect.  As we can see, there is some improvement in free throw shooting early in a player’s career.  After year 4 or 5 this improvement seems to stop.  Nevertheless, early on players appear to get better.

It’s possible, though, that this may not be due to coaching.  I didn’t just look at players who played all 10 seasons.  No, my data set includes anyone who played a season and attempted at least 100 free throws.  One suspects that weaker players are eliminated before they gain much experience.  Therefore, the relatively poor free throw shooting we see with less experience may just reflect that the data from inexperienced players includes a number of athletes who are not good enough to stick around.  And these players may tend to be poor free throw shooters.

Now I could just eliminate from my data set players who didn’t last.  But that would require more effort than I wish to put into this blog post.  A simpler approach is to rely on a data set I used for another study.  Specifically, I have data from 1991-92 to 2003-04 that looked at both current and lagged performance NBA performance.  Looking at this data set I found a correlation of 0.78 between current and lagged free throw percentage. 

In the past I have looked at correlations across time in baseball, football, and even hockey.  It’s simply not very common to find a correlation as high as we see for free throw percentage in professional team sports.  In sum, it appears to me that free throw percentage — relative to what we generally see when we look at performance across time in professional sports — is not something that varies much in a player’s career. 

What’s interesting about this result is that it seems like free throw shooting is something coaches could try and fix.  Certainly there are consultants who claim they can improve a player’s performance at the line.  But the data suggests that free throw shooting is not something that generally changes very much.

And maybe that shouldn’t be too surprising.  Players start shooting free throws when they are very young.  Players must notice that they are not good at shooting free throws in high school and college.  One would think that if this is something you could easily fix, it would be fixed in high school or college.  But this doesn’t seem to be happening.

In sum, it doesn’t look like changing Charlotte’s performance at the line really would have mattered for Vincent.  And furthermore, even if it did matter, it doesn’t look like coaches have much impact on free throw shooting.    

By the way, for more on how free throws can impact productivity see

The Best NBA Center in my Students’ Lifetime (looks at Shaq’s free throw shooting)

The Changing Fortunes of Jamal Magloire and Zach Randolph (looks at Magloire’s free throw shooting)

And for more on the Charlotte Bobcats in 2007-08 see

Okafor Finally Signs

UPDATE: I wrote this post on Monday night (clearly quite late on Monday night).  Now in the clear light of morning, I am not sure I like the second part of this post.  The first part seems right. Charlotte hitting more free throws would not have dramatically changed the team’s fortunes.  But the evidence presented in the second half doesn’t necessarily convince me that a coach is unable to impact a player’s free throw shooting.  I do like the argument that if players could change this aspect of their game, it would be changed before they got to the NBA.   But the approach taken to “test” the impact of coaches isn’t the best (and no, I don’t feel like trying any harder). All that being said, I think it is interesting that free throw shooting appears farily consistent over time (so the post has some value).  

– DJ

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Our research on the NBA was summarized HERE.

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Wins Produced, Win Score, and PAWSmin are also discussed in the following posts:

Simple Models of Player Performance

Wins Produced vs. Win Score

What Wins Produced Says and What It Does Not Say

Introducing PAWSmin — and a Defense of Box Score Statistics

Finally, A Guide to Evaluating Models contains useful hints on how to interpret and evaluate statistical models.