Do the Rockets need an Elite Shot Blocker?

From the perspective of a player, when factors such as pride are involved, getting blocked is something that must be avoided at all costs.  The roots of modern basketball (and a great number of NBA players) trace back to pickup games and playground-style rules where fouls do not lead to free throws and getting blocked is a point of embarrassment.  The smarter players can overcome this instinctual aversion and understand that challenging defenders around the rim leads to more free throws.  Not surprisingly these players are said to be “fundamentally sound,” and often are products of excellent coaching or European influence.

On the other end of the court, one aspect of being “undisciplined” defensively, somewhat synonymous with being “raw”, is the uninhibited impulse to block every shot.   When there aren’t any refs, the risk-reward relationship of attempting to block a shot shifts significantly in favor of going for the block.  Concurrently, the influence of pickup basketball rules changes a player’s perceived risk-reward relationship between driving to the rim and pulling up for a lower-percentage shot.  When the opportunity of free throw attempts is removed, a slight boost in FG% for shots around the rim versus, say, a 10-foot jump shot, does not justify the immense social risk of getting rejected.  My hypothesis is that, despite logic and best efforts of a coaching staff to keep players “disciplined” offensively, many players in the NBA cannot control their aversion to getting blocked, and therefore attempt lower-percentage shots.  These low-percentage shots include, in order of increasing egregiousness: raising the arc on a shot to clear the shot-blocker, shooting a fade-away, altering the shot/shooting form in mid-air, attempting a “floater” when there is a possible lane to the rim, and avoiding the drive all together and jacking up a long 2-pointer.

Opponent Shooting Percentage vs. Team Blocks

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The first step in my analysis was to see if there was a correlation between team block rate and opponent shooting percentage.  The idea is that if your team blocks a bunch of shots, opponents will not only miss those shots that were blocked, but will also have a large number of altered shots (assumed to be of greater difficulty and a lower shooting percentage).   Looking at regular-season data from 1999-2009 (, there appears to be a decent relationship, as displayed in the graph.   As you can see, as a team blocks more shots (block rate is blocks divided by opponent’s 2-point FGA), their opponents shoot at a lower percentage (ρ = -41.08%, rsq = 16.9%).

Opponent Shooting Location vs. Team Blocks

So we know that there is a relationship between opponents’ shooting and team shot blocking.  That was the first part of the theory.  The second part was that the FG% is lower because of an aversion to drive all the way to the basket.  The best way to measure that is to compare team shot blocking to opponent shooting locations.  I compared team block rates to two different location attempt percentages defined by (2006-2009) – “at rim” and “<10 feet” (for example, the “at rim” location attempt percentage would be attempts at rim divided by all 2-point attempts; in other words, the percentage of 2-point attempts at the rim).    To my initial surprise, there was a slightly negative correlation between opponents’ at rim attempt percentage and team block rate (ρ = -12.38%, rsq = 1.5%).  It makes sense, as more chances to block shots will obviously result in more blocks; however the relationship is pretty weak.   I then compared the same team block rate to the “<10 feet” attempt percentage.  The results were even more unimpressive (ρ = -3.2%, rsq = .1%).

What does all that mean?  It means that, despite a team blocking shots at a high rate, opponents do not change their shot locations.  My theory that players will tend to stop short and pull up instead of go all the way to the rim when driving against strong shot blockers was incorrect.  They still will attempt those shots.

But what about the FG% thing?  I showed earlier that block rate has a decently strong relationship with opponents’ FG%.  I just showed that that relationship has little to do with shot location, so what else could it be?  Taking a further look at the breakdown in opponent’s FG% by location, you can see what is happening:

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To my best understanding, the biggest effect of strong team shot blocking is altering shots near the rim.  The closer an attempt is to the rim, the greater effect a team’s block rate has on opponent shooting.  For “at rim” attempts, we see the most drastic dip in FG% (ρ = -46.48%, rsq = 21.67%).  It seems that shot blockers also affect “<10 Feet” shots as well, but not as much (ρ = -32.99%, rsq = 10.88%).  Conventional wisdom preaches the benefits of shot blockers altering shots, but this is the clearest evidence actually supporting that claim.

Opponent Shooting Location vs. Best Shot Blocker (Elite Blocker Theory)

Despite my best efforts to encourage basketball viewership from a team perspective, it is widely more popular (and fun) to look at individual players.   After all, when you’re driving to the rim against the Magic, are you thinking about Orlando’s team block rate or are you thinking about Dwight Howard throwing your shot into the bleachers?   I scanned through the same four seasons, and found the leading shot blocker on each team each year (minimum 65 games), using blocks per game.  I chose blocks per game over block rate to place weight on minutes played.  After all, a player’s “presence” cannot be felt if he isn’t on the floor very much.  I then did the same comparison as the previous section.  Predictably, there is a similar lack of meaningful relationship between the best player’s blocks per game and opponent shot attempt location.  However, just like team block rate, there is a relationship worth considering for FG% at the rim (ρ = -35.99%, rsq = 12.95%) and FG% <10 feet (ρ = -19.46%, rsq = 3.79%):

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As you can see, having an elite shot blocker clearly affects opponents’ shooting, and can explain a large part of a team’s block rate, especially at the rim.   If you read my first post, you know how important shooting efficiency is to winning.   Good teams hold opponents to a low FG%, and good shot blockers hold opponents to a low FG%.  So, exactly how important is it that your team is good at blocking shots?

Block Rate to Wins

To keep this all in perspective, I compared block rate to wins from 1999-2009.   Compared to some of the more prominent categories discussed in past posts, blocks are not very significant.  However, there is a positive correlation, with an r-squared of 6.7%.   Here is a graph showing the relationship between wins and block rate:

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While blocking more shots may make a minor contribution to wins, it is directly related to one of the Rockets’ biggest weaknesses – opponent shooting. That weakness is further compounded by abysmal perimeter defense, allowing opposing wing players to penetrate with ease.

Through 11/17, opponents were shooting 63.7% at the rim against the Rockets, above the league average of 62.4%.   In case you were curious, Howard and the Magic are holding their opponents to 54% at the rim, the lowest rate in the league.

The bottom line is Jordan Hill needs more playing time.  All of this business about him being a liability offensively needs to stop.   He is shooting 70.8% on inside shots, with only 53% of them coming from assists (which means that he is creating about half of his own shots inside, and still shooting 71%; sounds pretty good to me).  As I mentioned last week, one of the biggest reasons he cannot stay on the floor is his poor court awareness and defensive rotations.  As soon as he can work out those kinks, I think he can provide the interior help that we have been lacking most of the season.

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